From the Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Peptidoglycan recognition protein (PGRP)
specifically binds to peptidoglycan and is considered to be one of the
pattern recognition proteins in the innate immunity of insect. The PGRP
is an essential component for peptidoglycan to trigger the
prophenoloxidase cascade that is now recognized to be an important
insect defense mechanism. We cloned cDNA encoding PGRP from the
silkworm fat body cDNA library. Northern blot analysis showed that
the PGRP gene is constitutively expressed in the fat body, epithelial
cell, and hemocytes of naive silkworms. Furthermore, a bacterial
challenge intensified the gene expression, with the maximal period
being from 6 to 36 h after infection. The upstream sequence of the
cloned PGRP gene was shown to contain putative
cis-regulatory elements similar to the NF- Innate immunity plays vital roles in primary defense mechanisms
against invading pathogens in both vertebrates and invertebrates. The
common structures among pathogens are recognized to be non-selves in
the immunity. This type of recognition is termed pattern recognition, as opposed to clonal recognition in which clonally selected
immunoglobulins are employed (1). Lipopolysaccharide
(LPS)1 and peptidoglycan (PG)
are the cell wall components of bacteria and Among the pattern recognition proteins in mammals, a humoral
LPS-binding protein and the cellular receptor CD14 have been well
characterized (2-5). Their roles in stimulating macrophages to produce
cytokines are well understood. In contrast, pattern recognition
proteins for PG and In insects, a number of proteins that could be pattern recognition
proteins have been described. They are lectins (8-11), hemolin (12,
13), lipopolysaccharide-binding protein (14, 15), Gram-negative
bacteria-binding protein (16), peptidoglycan recognition protein (PGRP)
(17), and It is not clear whether pattern recognition proteins with the same
specificity in mammals and in insects have any common structural similarity. However, parallels between cellular signaling pathways for
the synthesis of mammalian acute phase proteins and insect immune
proteins after a bacterial challenge have been revealed (21). This
indicates a common origin of the pathways in innate immunity in mammals
and insects
Here, we report the cloning of PGRP cDNA from the fat body cDNA
library and PGRP gene from the genomic library of the silkworm Bombyx mori. The homology search showed that PGRP is a
homologous protein to bacteriophage T7 lysozyme, although it does not
have lysozyme activity, and that proteins homologous to PGRP are
expressed in mammals. This experimental evidence suggests that
recognition proteins for the initial extracellular non-self recognition
in innate immunity of vertebrates and invertebrates have developed from
a common origin. Our experimental results also show that PGRP synthesis
is induced by a bacterial challenge and suggest that expression of the
PGRP gene is regulated by the Rel family of transcription factors.
Insect and Bacterial Challenge--
Silkworms, B. mori (strain Kinshu × Showa), were reared on an artificial
diet as described previously (22). The larvae on day 5 of the fifth
instar were injected with 10 µl of late logarithmic phase
Enterobacter cloacae (JCM1232) suspension
(A600 = 0.1) in the physiological saline
(10 mM bis-Tris propane buffer, pH 6.5, containing 150 mM NaCl) or with 10 µl of the saline as the control experiment.
Purification and Amino Acid Sequencing of PGRP--
PGRP was
purified as described by Yoshida et al. (17).
S-Pyridylethylated or intact PGRP was digested with trypsin
at a molar ratio of enzyme to substrate of 1:50. The digestion was carried out in 0.1 M Tris-HCl, pH 6.5, at 37 °C for
24 h, and the resulting peptides were separated by high
performance liquid chromatography on a C8 column (4.6 × 150 mm, Vydac). The isolated peptides were sequenced using an
automatic protein sequencer (Shimadzu PSQQ-10). The sequences of the
peptides derived from S-pyridylethylated or intact PGRP were
compared to determine the disulfide bond locations.
Cloning and Sequencing of PGRP cDNA--
A silkworm fat body
cDNA library was constructed in the vector Northern Blot Analysis--
In the detection of PGRP transcript
in naive silkworms, poly(A)+ RNA preparations from
hemocytes, fat body, epidermal cells, midgut, silk gland, and
malpighian tubules were prepared by chromatography on
oligo(dT)-cellulose (Amersham Pharmacia Biotech). 5 µg of
poly(A)+ RNA of each preparation were separated by
electrophoresis in 1% agarose gels with 10 mM sodium
phosphate, pH 7.0, transferred to a Hybond-N+ (Amersham Pharmacia
Biotech) membrane, and hybridized with a 32P-labeled PGRP
cDNA probe. The hybridization was performed for 16 h at
42 °C in 50% formamide, 4 × SSPE (1.2 M NaCl, 40 mM sodium phosphate, pH 7.4, and 4 mM EDTA),
5 × Denhardt's (0.1% polyvinylpyrrolidone, 0.1% bovine serum
albumin, and 0.1% Ficoll), 0.1% SDS, and 100 µg/ml denatured salmon
sperm DNA. The membrane was washed once in 2 × SSPE containing
0.1% SDS and subsequently twice in 1 × SSPE containing 0.1% SDS
at 56 °C for 10 min. In the experiments to demonstrate the induction
of PGRP gene in the fat body, total RNA from the fat body of silkworms
was collected at intervals after the bacterial challenge. 20-µg
aliquots of the RNA preparations were subjected to Northern blot
analyses as above except that silkworm cecropin B (0.4 kbp) (23) and
Southern Blot Analysis--
Silkworm genomic DNA was isolated
from the silk gland using DNzol (Life Technologies, Inc.), and 10 µg
of the DNA were digested with EcoRI, BamHI, or
SacI. DNA fragments in the digests were separated by
electrophoresis on a 0.8% agarose gel, blotted onto Hybond-N+
membrane, and hybridized with the
32P-EcoRI/KpnI-digested cDNA. The
digested cDNA probe (0.77 kbp) was the entire insert of PGRP
cDNA clone with short flanking sequences. The conditions for the
hybridization and the washings were the same as those in Northern blot analysis.
Analysis of PGRP Gene Structure--
2 × 105
plaques of an amplified B. mori genomic library constructed
in Nucleotide Sequence of PGRP cDNA and the Deduced Amino Acid
Sequence--
PGRP cDNA clones were obtained by screening a fat
body cDNA library of the silkworm B. mori. The
nucleotide sequence and the deduced amino acid sequence are shown in
Fig. 1. The open reading frame composed
of nucleotides 31-618 encodes 196 amino acid residues. The first 23 amino acid residues seemed to be a signal peptide because the deduced
amino acid sequence beginning from the 24th residue was identical to
that observed previously at the N terminus of PGRP. Thus, the mature
protein consists of 173 residues with a calculated molecular mass of
19290 Da. 49% of the deduced mature protein sequence, including the
N-terminal, was confirmed to be identical to that determined by direct
sequencing of peptides obtained after trypsin digestion of PGRP (Fig.
1). Consensus sequence for N-glycosylation was not found in
the deduced sequence. A polyadenylation consensus signal was not
observed downstream of the stop codon. The cysteine residues engaged in
the formation of the disulfide bond were determined to be
Cys2-Cys124 and
Cys38-Cys44 from a comparison of the results of
peptide mapping and amino acid sequencing of reduced and nonreduced
PGRP.
Expression of PGRP mRNA--
Northern blot analysis using PGRP
cDNA as a probe detected a 0.8-kbp transcript of PGRP in hemocytes,
fat body, and epidermal cells but not in malpighian tubules, silk
gland, and midgut of naive silkworms. This result indicates that PGRP
mRNA is constitutively expressed in the fat body, epidermal cells,
and hemocytes. Major sites for the synthesis of PGRP seemed to be the
fat body and epidermal cells (Fig.
2A). The expression of PGRP
gene and cecropin B gene in fat body was induced by injection of
bacteria (E. cloacae) to silkworm larvae, as shown in Fig.
2B. The induction kinetics was similar in both genes: the
induction was detected at 6 h and reached its maximum at 24 h
after injection. When saline was injected instead of bacteria in the
above Northern analysis, neither of the transcripts of PGRP and
cecropin B genes increased in the fat body for 36 h after the
injection (data not shown). These results indicated that the expression
of PGRP gene is inducible by a bacterial challenge and that PGRP could
be classified as an acute phase protein. We could detect the induction
of PGRP gene expression in the fat body by the injection of
Micrococcus luteus
peptidoglycan.2
Structure of PGRP Gene--
We isolated three positive clones from
the silkworm genomic library. The restriction maps of the three clones
indicated that a 2.1-kbp SacI fragment overlaps both the
2.5- and 4.3-kbp BamHI fragments (Fig.
3B). Both of the
BamHI fragments and the 2.1-kbp SacI fragment
were subcloned separately into pBluescript. The sequences of these
fragments were examined after subcloning the various restriction
fragments. By comparison of the nucleotide sequence of the PGRP gene
with that of the PGRP cDNA clone, the PGRP gene was revealed to
contain four exons (exon I, nucleotides 1-100; exon II, 101-299; exon
III, 300-418; and exon IV, 419-739 by nucleotide numbering of the
PGRP cDNA clone in Fig. 1) interspersed with three introns. The 5'
end of exon I is putative because the starting point of transcription
of the PGRP gene has not been studied. The 2.5-kbp BamHI
fragment contained 1966 bp of 5' upstream sequence of the initiating
Met codon (Fig. 3C). The TATA-box (TATATA) is located from
nucleotide
Southern blot analyses of genomic DNA digested with EcoRI,
BamHI, or SacI were performed by using the PGRP
cDNA probe. As is shown in Fig. 3A, only one hybridized
band was observed with the digest by EcoRI or
BamHI, and the digest with SacI gave two hybridized bands (2.1 and 6.0 kbp). Because the cloned PGRP gene had
one restriction site for each of BamHI and SacI,
the digest with BamHI should have given two hybridization
bands (2.1 kbp in addition to the observed 6.0 kbp). The reason we
could not observe the 2.1-kbp fragment seems to be that the fragment
contains only a short exon and the PGRP cDNA probe barely
hybridized with the fragment. Thus, the results of the Southern blot
analyses indicate the presence of a single copy of the PGRP gene in the silkworm genome.
Search for the Homologs of PGRP--
We searched for the existence
of silkworm PGRP homologs in the data base sequences by BLAST and found
that an expressed sequence tag from the lymphatic filarial nematode
Brugia malayi, and sequences of bacteriophage T7 lysozyme
and mouse Tag7 protein are homologous to silkworm PGRP (Fig.
4). Furthermore, the Drosophila
melanogaster gene encoding RNA polymerase II (M27431) was found to
contain a PGRP-like sequence. The sequence is in the complementary
strand of RNA polymerase II-coding sequence and corresponds to 140 bp from the end of the registered sequence (Fig. 4).
We have previously reported the purification and characterization
of the PGRP from the hemolymph of the silkworm B. mori (17). The PGRP specifically binds to peptidoglycan, and this binding leads to
activation of the prophenoloxidase cascade in the plasma fraction of
the silkworm hemolymph. In the present study, we cloned PGRP cDNA
and the gene.
The cloned PGRP cDNA contained an open reading frame (nucleotides
31-618) encoding a protein with 196 amino acid residues. The deduced
amino acid sequence of the protein had a putative 23-amino acid signal
sequence and a mature protein sequence. The molecular mass (19290 Da)
calculated from the primary structure of the deduced mature protein is
in good agreement with the value (19 kDa) determined before by
SDS-polyacrylamide gel electrophoresis of purified PGRP. The absence of
N-glycosylation consensus sequence in the deduced amino acid
sequence of PGRP is consistent with our previous observation that
purified PGRP did not manifest reactivity to eight commercially
available lectins. We have produced recombinant PGRP in a baculovirus
expression system and confirmed that the protein possesses the ability
to specifically bind to
peptidoglycan.3 This
observation supports further that our cloned cDNA encodes PGRP.
Among proteins of which the sequence and function are known,
bacteriophage T7 lysozyme is the only protein interacting with peptidoglycan and having the sequence similarity with PGRP.
Furthermore, the amino acid residues of PGRP corresponding to the five
catalytically active residues of the lysozyme (25) were all replaced
with other amino acids. Considering the ability of PGRP to bind to peptidoglycan, the homology is understandable. At the same time, the
present results concerning the PGRP sequence did not offer any clues to
answering our question: What kind of activity does the complex of PGRP
and peptidoglycan have? Because binding of PGRP to peptidoglycan is
known to lead to the activation of protease zymogens of the
prophenoloxidase cascade, we had speculated that PGRP itself is a
protease zymogen of which activation is caused by its binding to
peptidoglycan. However, the deduced PGRP sequence seemed to deny this
possibility. We now speculate that the complex of peptidoglycan and
PGRP activates a protease zymogen that is a member of the
prophenoloxidase cascade. In the blood coagulation system of horseshoe
crab, the factors that directly interact with elicitors such as
lipopolysaccharide and Our search for proteins with the sequence similarity to PGRP indicated
that homologs to PGRP are present in mice and nematodes. The mouse Tag7
protein has been reported to be a cytokine (27). It remains to be
determined whether the silkworm PGRP has a similar biological activity.
The ancestral protein of the homologs to PGRP seems to have appeared
before protostomia and deuterostomia diverged in evolution and to be
present widely in animals. This wide distribution of PGRP suggests the
possibility that insect PGRP and its homologs may generally play a role
in the recognition of peptidoglycan in innate immunity. The function of
PGRP in triggering the prophenoloxidase cascade may be peculiar to
insects. Peptidoglycan manifests various biological activities as have
been mentioned in the introduction of our previous paper (17) and of
papers by Dziarski and co-workers (6, 7). Despite the myriad
activities, the mechanism for the recognition of peptidoglycan as
foreign has been poorly understood. Recently, Dziarski and co-workers showed that CD14 on murine macrophages has affinity to peptidoglycan and is involved in activation of the transcription factor NF- A single copy of the PGRP gene was indicated to be present in the
silkworm genome (Fig. 3A). We detected a cAMP response
element, NF- The intracellular events leading to the induction of acute phase immune
protein synthesis are now being intensely studied in both insects and
mammals. Proteins belonging to the Rel family are commonly employed in
the signaling pathway for the induction in different organisms (21, 30,
31). Toll has been shown to be a receptor for a protein named
spätzle and to participate in the signaling for the activation of
Drosophila immune protein gene coding for drosomycin (32).
Recently, a Toll homolog has been reported to be involved in human
innate immunity as well as adaptive immunity (33). All these
observations point to a common origin of the intracellular signaling
pathway. Our present results indicated the presence of homologous
pattern recognition proteins for peptidoglycan in both insects and
mammals. The results seem to imply that the mechanism for extracellular
recognition of microbes as foreign is conserved between insects and
mammals, indicating a yet closer relation between innate immune systems in such phylogenetically remote organisms as insects and mammals.
B-like
element, interferon-response half-element, and GATA motif element,
which have been found in the promoters of the acute phase protein genes
of mammals and insects. A homology search revealed that the homologs of
silkworm PGRP are present in mice, nematodes, and bacteriophages. This
suggests that the recognition of peptidoglycan as foreign is effected
in both vertebrates and invertebrates by PGRP homologs with an
evolutionally common origin.
INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS
DISCUSSION
REFERENCES
-1,3-glucan (
G) is
that of fungi. They are recognized by pattern recognition proteins that
are present in plasma as free-floating molecules or on the cell surface
as receptors.
G have not been characterized as thoroughly as
those for LPS, although CD14 is also implicated for the recognition of
PG as non-self (6, 7).
-1,3-glucan recognition protein (
GRP) (18, 19). The
latter two proteins are members of the prophenoloxidase cascade, of
which other members are known to be serine protease zymogens and
prophenoloxidase (20). They have been shown to have specific affinity
to PG or
G and to work at initiation points of the cascade. The
prophenoloxidase cascade is now recognized to be one of major insect
defense mechanisms and to possibly play vital roles in interrelating
the mechanisms and in recognizing of microbes as foreign. Thus, it is
probable that PGRP and
GRP of the prophenoloxidase cascade are
employed generally in insects as pattern recognition molecules for PG
and
G. We previously reported the purification and the
characterization of silkworm PGRP and
GRP (17, 18). Pattern
recognition proteins other than PGRP and
GRP are not known to be
distributed among insects as widely as PGRP and
GRP.
EXPERIMENTAL PROCEDURES
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS
DISCUSSION
REFERENCES
ZAP (Stratagene).
Using internal peptide sequences, degenerate oligonucleotides
corresponding to KKQWDG and WPEWLE were synthesized. Their sequences
were 5'-AAGAATTCAA(A/G)AA(A/G)CA(A/G)TGGGA(C/T)GG-3' (sense
primer) and 5'-AAGAATTCTC(A/C/G/T)A(A/G)CCA(C/T)TC(A/C/G/T)GGCCA-3' (antisense primer), respectively. These primers were used for the
polymerase chain reaction. The reaction was performed using the
silkworm fat body cDNA library as a template under the following conditions: 35 cycles comprising 94 °C for 1 min, 60 °C for 2 min, and 72 °C for 3 min. A 480-bp fragment was amplified, subcloned into a plasmid vector pBluescript (Stratagene), and sequenced using an
automatic DNA sequencer (PE Applied Biosystems, model 377). The cloned
polymerase chain reaction product labeled with [
-32P]dCTP was used to probe the
ZAP fat body
cDNA library. Hybridization was carried out at 42 °C for 16 h in 2 × PIPES buffer (0.8 M NaCl, 40 mM
PIPES, pH 6.5), 50% formamide, 0.5% SDS, and 100 µg/ml denatured salmon sperm DNA. The membrane was washed twice in 0.1 × SSC (15 mM NaCl, 1.5 mM sodium citrate, pH 7.2) at
53 °C for 15 min and subjected to autoradiography. Three positive
clones were obtained and sequenced. The clone that had the longest
insert and a complete open reading frame was used as PGRP cDNA clone.
-tubulin (1.3 kbp) probes were used in addition to the PGRP probe.
The silkworm cecropin B (0.4 kbp) and
-tubulin (1.3 kbp) probes were
obtained as polymerase chain reaction products, and the identities of
their sequences to those having been reported were confirmed by
referring to GenBankTM accession numbers S60579 and X83429, respectively.
FIX (Stratagene) were screened with the 32P-labeled
PGRP cDNA probe. Three positive plaques were isolated, and the
DNA was digested with BamHI or SacI. The
32P-labeled PGRP cDNA probe hybridized with 2.5- and
4.3-kbp DNA fragments of BamHI digest and with a 2.1-kbp
fragment of SacI digest. All the fragments were separately
subcloned into pBluescript. After the deletion clones of the subclones
were prepared, they were sequenced. Computer analysis of the sequencing
data was performed using the GENETYX system (Software Development Co.,
LTD Tokyo).
RESULTS
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS
DISCUSSION
REFERENCES
View larger version (59K):
[in a new window]
Fig. 1.
Nucleotide sequence of cDNA encoding PGRP
from B. mori and the deduced amino acid
sequences. The amino acid sequence is numbered at
right, beginning at the N terminus of the mature protein,
and the nucleotide sequence is numbered at left.
Underlined amino acid residues were confirmed by sequencing
of the N terminus of the mature protein and the peptide fragments which
obtained after proteolysis of the S-pyridylethylated PGRP by
trypsin.
View larger version (47K):
[in a new window]
Fig. 2.
Tissue-specific expression
(A) and inducibility (B) of PGRP
mRNA by Northern blot analysis. A,
poly(A)+ RNA were isolated from tissues of silkworm larvae
at day 5 of the fifth instar. 5 µg of poly(A)+ RNA was
loaded on each lane. Lanes to which the poly(A)+ RNA
preparations were loaded and the sources of the poly(A)+
RNA were as follows: H, hemocytes; F, fat body;
E, epidermal cell; MT, malpighian tubules;
S, silk gland; MG, midgut. B, silkworm
larvae at the same developmental stage as in A were
challenged by E. cloacae as described under "Experimental
Procedures." Total RNA was extracted from the fat body at the
indicated times after infection. Total RNA (20 µg) was subjected to
Northern blot analysis where the blots were hybridized separately with
32P-labeled silkworm PGRP, cecropin B, and -tubulin
cDNA probes. The names of the probes are indicated at the
left of the figure.
73 to
68. Several putative cis-regulatory sequences were observed within
210 bp from the TATA-box. They were
cAMP response motif (GTGACGTCAC), NF-kB-like motif (AGGGATTTCC), GATA
motif (TGATAA), and five interferon response half-motifs (GAAANN) that
have been found in promoter regions of many acute phase protein genes
(24).
View larger version (63K):
[in a new window]
Fig. 3.
The PGRP gene. A, Southern
blot analysis of B. mori genomic DNA digested with
EcoRI, SacI, or BamHI. 10 µg of the
digested DNA was separated on 0.8% agarose gel, blotted onto a nylon
membrane, and hybridized with the
32P-EcoRI/KpnI-digested PGRP
cDNA. B, schematic representation of the genomic clone
of PGRP. Open boxes with Roman numerals represent
exons, and restriction enzyme sites are indicated by their names and
arrows. C, the nucleotide sequence of the
SacI-BamHI genomic fragment containing exon I of
the PGRP gene. Nucleotides are numbered from the A of the translation
start codon (position +1). Exon I is double-underlined, and
the deduced amino acid sequence for PGRP is shown below the nucleotide
sequence in single-letter code. The putative TATA box and various
cis-regulatory elements are underlined with their
names.
View larger version (52K):
[in a new window]
Fig. 4.
Sequence alignment of silkworm PGRP with the
homologs from the GenBankTM data base. The shown
sequences, except B. mori PGRP, were obtained from the data
base: D. melanogaster PGRP, M27431; nematode-expressed
sequence tag, AA228200; mouse Tag7, X86374; T7 lysozyme, S75616.
Alignments were done with the CLUSTAL V program. Gaps (indicated by
hyphens) are inserted to maximize sequence alignment, and
amino acid residues identical to silkworm PGRP are boxed.
Percentage identities referred to silkworm PGRP are indicated.
DISCUSSION
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS
DISCUSSION
REFERENCES
-1,3-glucan are zymogen of proteases (26). In
this respect, the component located at the initiation point of the
prophenoloxidase cascade is different from that of the blood
coagulation cascade.
B by
peptidoglycan (7). It has been established that CD14 is a receptor for
LPS in mammals (3). In this case, however, another protein, the
LPS-binding protein, in plasma is assumed to form a complex with LPS,
and KD of CD14 for the complexed LPS becomes very
low in comparison with that for noncomplexed LPS. Thus, the LPS-binding
protein increases the sensitivity of cells with CD14 to LPS. It would
be worth testing whether PGRP works in the same way as the LPS-binding protein.
B-like element, and five interferon response
half-elements in the promoter region of the gene. The transcripts of
the gene were detected in the fifth instar larvae before challenging
them with Gram-negative bacteria or peptidoglycan. However, the
transcription was up-regulated after challenging them with the microbes
or the cell wall component (Fig. 2). The presence of
cis-regulatory elements like an NF-
B element and the
enhancement of transcription by cell wall components of microbes are
common features of acute phase proteins of insects and mammals (28,
29). In this respect, PGRP can be classified to be an acute phase
immune protein. Whether up-regulated expression of the PGRP gene upon
bacterial challenge has merits for silkworms and, if so, what those
merits are remain to be studied.
![]() |
Addendum |
---|
After the submission of the manuscript of the present paper, a paper reporting a cDNA for PGRP from a moth Trichoplusia ni and its mouse and human homologs was published (34).
![]() |
FOOTNOTES |
---|
* This work was supported in part by Research Grants 07740641, 09265201, and 09304075 from the Ministry of Education, Science, Sports and Culture of Japan.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EMBL Data Bank with accession number(s) AB016249 and AB016605.
To whom correspondence should be addressed: Inst. of Low
Temperature Science, Hokkaido University, Sapporo 060-0819, Japan. Tel.: 81-11-706-6878; Fax: 81-11-706-7142; E-mail:
ochiai{at}orange.lowtem.hokudai.ac.jp.
2 M. Ochiai, unpublished observation.
3 T. Nomura, T. Kanaya, and M. Ochiai, unpublished observation.
![]() |
ABBREVIATIONS |
---|
The abbreviations used are:
LPS, lipopolysaccharide;
PG, peptidoglycan;
G,
-1,3-glucan;
PGRP, peptidoglycan recognition protein;
GRP,
-1,3-glucan recognition
protein;
T7 lysozyme, N-acetylmuramoyl-L-analine
amidase (EC 3.5.1.28);
bp, base pair(s);
kbp, kilobase pair(s);
PIPES, 1,4-piperazinediethanesulfonic acid.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|