Putative antimicrobial protein

Xanthomonas citri pv. punicae (Xcp) is the causative agent of bacterial blight disease in pomegranate and severely affects its production. The current control strategies for this disease provide inadequate protection. Identifying novel bactericide target proteins in pathogenic bacteria and formulating selective chemicals against those proteins is an effective approach to containing the disease. In this study, we used the genome subtraction approach and identified 595 Xcp proteins that are non-homologous to the pomegranate proteome, of which 69 are found to be essential proteins. These 69 proteins are considered possible drug target proteins in Xcp. Further, these proteins were subjected to subcellular localization, KEGG pathway, and virulent prediction analysis. Our systematic bioinformatics analysis deciphered 33 virulent proteins, of which two are iron complex outer membrane receptors, and the third is a T4SS PilQ protein localized in the outer membrane. These outer membrane-localized proteins are potential candidate targets for antibacterial agents, and the two iron complex outer membrane receptor proteins show homology with the Drug bank listed drug target sequences. From this study, we inferred that PilQ could be considered a novel antimicrobial target of Xcp, and therefore we deciphered the PilQ protein-protein interacting partners and phylogenetic relatedness. We have also predicted the physiochemical properties, secondary, and tertiary structure of PilQ protein which will be helpful in the design of antimicrobials. The identification of Xcp specific targets is the first step towards the development of a chemical control agent that is more selective with minimum environmental impact.

Chemokines are a family of small signaling proteins that are secreted by various cells. In addition to their roles in immune surveillance, localization of antigen, and lymphocyte trafficking for the maintenance of homeostasis, chemokines also function in induce immune cell migration under pathological conditions. In the present study, a novel CC chemokine gene (CaCC1) from humpback grouper (Cromileptes altivelis) was cloned and characterized. CaCC1 comprised a 435 bp open reading frame encoding 144 amino acid residues. The putative molecular weight of CaCC1 protein was 15 kDa CaCC1 contains four characteristic cysteines that are conserved in other known CC chemokines. CaCC1 also shares 11.64%-90.28% identity with other teleost and mammal CC chemokines. Phylogenetic analysis revealed that CaCC1 is most closely related to Epinephelus coioides EcCC1, both of which are in a fish-specific CC chemokine clade. CaCC1 was constitutively expressed in all examined C. altivelis tissues, with high expression levels in skin, heart, liver, and intestine. Vibrio harveyi stimulation up-regulated CaCC1 expression levels in liver, spleen, and head-kidney. Functional analyses revealed that the recombinant protein (rCaCC1) could induce the migration of head-kidney lymphocytes from C. altivelis. Moreover, rCaCC1 significantly enhanced phagocytosis in head-kidney macrophages from C. altivelis. In addition, rCaCC1 exhibited antimicrobial activities against Staphylococcus aureus, Edwardsiella tarda, and V. harveyi. In vivo, CaCC1 overexpression improved bacterial clearance in V. harveyi infected fish. Conversely, CaCC1 knockdown resulted in a significant decrease of bacterial clearance. These results demonstrate the important roles that CaCC1 plays in homeostasis and in inflammatory response to bacterial infection.

The soaring incidences of infection by antimicrobial resistant (AR) pathogens and shortage of effective antibiotics with new mechanisms of action have renewed interest in phage therapy. This scenario is exemplified by resistant tuberculosis (TB), caused by resistant Mycobacterium tuberculosis. Mycobacteriophage SWU1 A321_gp67 encodes a putative GTPase-activating protein. Mycobacterium smegmatis with gp67 overexpression showed changed colony formation and biofilm morphology and supports the efficacy of streptomycin and capreomycin against Mycobacterium. gp67 down-regulated the transcription of genes involved in cell wall and biofilm development. To our knowledge, this is the first report to show that phage protein in addition to lysin or recombination components can synergize with existing antibiotics. Phage components might represent a promising new clue for better antibiotic potentiators.