Bacterial Peptides

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.