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Competence-Stimulating Peptide-2 (CSP-2) 是肺炎链球菌产生的群体感应信号肽。ComD2 是 Competence-Stimulating Peptide-2 (CSP-2) 的兼容受体，EC50 值为 50.7 nM。

Competence-Stimulating Peptide-2 (CSP-2) is a quorum sensing signal peptide produced by Streptococcus pneumoniae. ComD2 is a compatible receptor of Competence-Stimulating Peptide-2 (CSP-2) with an EC50 value of 50.7 nM.

CSP-2，能力刺激肽-2，序列为EMRISRIILDFLFLRKK的肽是肺炎链球菌、轻度链球菌和口腔链球菌的遗传转化，由分泌的肽信息素调节，称为能力刺激肽（CSP）。这些细菌的不同菌株和种类产生具有不同初级序列的CSP。其他CSP序列有：CSP-1（EMRLSKFRDFILQRKK）、CSP-153（DKRLPYFFKHLFSNRTK）、CSP-612（ESRLSRLLRDFIFQIKQ）、CSP-676（ERRIPDVIRSLLFQKRK）和CSP-12261（EIRQTHNIFFNFFKRR）。

CSP - 2, Competence - Stimulating Peptide - 2 peptide with sequence of EMRISRIILDFLFLRKK are genetic transformation in streptococcus pneumoniae, Streptococcus mitis and Streptococcus oralis is regulated by secreted peptide pheromones named the competence-stimulating peptide (CSP). Different strains and species of these bacteria produce CSP with different primary sequence. Other CSP sequence are: CSP-1 (EMRLSKFFRDFILQRKK), CSP-153 (DKRLPYFFKHLFSNRTK), CSP-612 (ESRLSRLLRDFIFQIKQ), CSP-676 (ERRIPDVIRSLLFQKRK), and CSP-12261 (EIRQTHNIFFNFFKRR).

Definition

Bacterial peptides are protein fragments which are either part of a bacterium or produced by a bacteria1.

Classification

Different classes of peptides are produced by bacteria. Some examples include, antibiotics, enterotoxins, flagellar proteins, lipoproteins and various enzymes1.

Structural Characteristics

Structural characteristics of some bacterial peptides are described below-

A)      Malaria merozoite surface peptide (MSP-1): It is synthesized as a large precursor on the surface of the bacterium Plasmodium falciparum.  Proteolytic cleavage results in the production of a 19 KDa product whose tertiary structure is maintained by disulphide bridges2.

B)     Giardia variable surface protein: This peptide is the specific conserved region of the Giardia variable surface proteins (VSPs) that are cysteine rich zinc finger proteins. VSPs differ in size and sequence, they are characterized by this highly conserved C-terminal membrane spanning region, a hydrophilic cytoplasmic tail with a conserved five amino acid CRGKA signature sequence3,4.

C)    P.falciparum liver stage antigen 3: The protein is 200Kda and is highly conserved among parasites from different geographic regions5.

Mode of action

A)     MSP-1 is known to trigger antibody response by CD4 helper T cells. It is likely that these cells bind to the C-terminal domain of MSP-12.

B)     VSPs have a conserved hydrophilic amono acid trail that is palmitoyted by palmityl tranferases upon which they are activated3,4.

C)    P. falciparum liver stage antigen 3 is a potent antigen that is recongnized by T cells5.

Functions

A)     MSP-1 is a vaccine candidate for Plasmodium falciparum infection. It triggers a CD-4 T cell response2.

B)     VSPs are necessary for survival in the environment and host infection3,4.

C)    P.falciparum stage antigen 3 is also a good candidate vaccine as it activates both T and B cell responses5.

References

1.     Gitai Z (2005). "The new bacterial cell biology: moving parts and subcellular architecture". Cell, 120 (5): 577–86.

2.     Stuart JQ and Jean L (2001). Different regions of the malaria merozoite surface protein 1 of Plasmodium chabaudi elicit distinct T-cell and antibody isotype responses. Infect Immun, 69(4): 2245–2251.

3.     Davids BJ, Reiner DS, Birkeland SR, Preheim SP, Cipriano MJ, McArthur AG, Gillin FD (2006). A New Family of Giardial Cysteine-Rich Non-VSP Protein Genes and a Novel Cyst Protein. PLoS ONE, 20,1:e44.

4.     Touz MC, Conrad JT, Nash TE (2005). A novel palmitoyl acyl transferase controls surface protein palmitoylation and cytotoxicity in Giardia lamblia. Mol Microbiol., 58 (4), 999-1011.

5.     Jean-Pierre S, Blanca LP, Karima B, Pierra D, Pierra D (2001). DNA Immunization by Plasmodium falciparum liver-stage antigen 3 induces protection against Plasmodium yoelii Sporozoite challenge. Infect Immun., 69, 1202–1206.

Yifang Yang, et al. Structural Characterization of Competence-Stimulating Peptide Analogues Reveals Key Features for ComD1 and ComD2 Receptor Binding in Streptococcus pneumonia. Biochemistry. 2018 Sep 11;57(36):5359-5369. : https://pubmed.ncbi.nlm.nih.gov/30125091