Identification and Characterization of a Novel GAPDH-Derived Antimicrobial Peptide From Jellyfish

Abstract

Marine organisms serve as a rich source of bioactive natural compounds, including antimicrobial agents. Jellyfish, which are ancient marine invertebrates with hundreds of millions of years of evolutionary history, have been in continuous contact with a diverse array of pathogenic microorganisms from seawater, which may give rise to a distinctive innate immune system and related defensive molecules. However, it is difficult and inefficient to isolate active ingredients directly from jellyfish for enrichment, though few jellyfish-sourced antimicrobial peptides (AMPs) have been reported. In this study, we utilized transcriptomic big data with bioinformatic tools to dig deeper into potential antimicrobial components in jellyfish, and identified a new AMP JFP-2826 from Rhopilema esculentum. The 20-mer peptide exhibited an alpha-helix structure and showed antimicrobial activity against selected bacterial strains; more importantly, JFP-2826 demonstrated good selectivity for marine-specific Vibrio including Vibrio vulnificus. Sequence analysis of the full-length protein of JFP-2826 revealed that it is derived from the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is probably produced through enzymatic cleavage of the N-terminal fragment. This suggests that GAPDH of jellyfish might have a newly discovered antimicrobial-related function that is conducted by releasing JFP-2826-like cryptic peptides. JFP-2826 can be subjected to further structural modifications and optimizations to potentially become a potent lead peptide for the development of novel antimicrobial drugs treating infections of marine pathogens.

Keywords: Vibrio vulnificus; antimicrobial peptide; bioinformatics; jellyfish; transcriptome.

FIGURE 1

Characterization and structure analysis of JFP‐2826. (A) Values of JFP‐2826 for the prediction of antimicrobial activity in E. coli, S. aureus and Vibrio vulnificus . (B) 3D conformation of JFP‐2826 using Phyre2 and PyMOL. (C) Secondary protein structural analysis of JFP‐2826. The peptide concentration was fixed at 50 μM. (D) Helical wheel diagram of JFP‐2826.

FIGURE 2

MIC of (A) Ampicillin and (B) JFP‐2826 against E. coli (ATCC 25922), S. aureus (ATCC 25923) and V. vulnificus (ATCC 27562), n = 3. *, p < 0.05, **, p < 0.01, ***, p < 0.001, ****, p < 0.0001 versus control.

FIGURE 3

Antimicrobial kinetics of JFP‐2826 and ampicillin. (A) E. coli (ATCC 25922), (B) S. aureus (ATCC 25923) and (C) V. vulnificus (ATCC 27562) were incubated with JFP‐2826 and ampicillin at 1 × MIC, 5 × MIC and 10 × MIC values.

FIGURE 4

Biofilm inhibition and eradication activities of JFP‐2826 and ampicillin. E. coli (ATCC 25922), S. aureus (ATCC 25923) and V. vulnificus (ATCC 27562) were treated with different concentrations of ampicillin (A) and JFP‐2826 (B) to measure the inhibition of biofilm formation. E. coli (ATCC 25922), S. aureus (ATCC 25923) and V. vulnificus (ATCC 27562) were treated with different concentrations of ampicillin (C) and JFP‐2826 (D) to measure the eradication of biofilm formation, n = 3. *, p < 0.05, **, p < 0.01, ***, p < 0.001, ****, p < 0.0001 versus control.

FIGURE 5

Prediction of complete protein sequences and cleavage sites of JFP‐2826. (A) Sequence of the full‐length protein of JFP‐2826. (B) Predicted cleavage sites of the full‐length protein. JFP‐2826 sequence was shown in red frame. (C) 3D structure model of the full‐length protein using Phyre2 and PyMOL.