The American lobster, H. americanus, is a commercially important crustacean that also plays an important role as a model organism for studying neuronal network responses, due to its relatively simple cardiac neuromuscular system. In this study, we report on the detection and characterization of a 4 kDa peptide, found in lobster hemolymph (circulatory fluid) and in eyestalk tissues using chip-based nanoESI liquid chromatography–tandem mass spectrometry (LC-MS/MS). To characterize this peptide and other lower molecular weight components of hemolymph, we have developed a method for preparing samples for LC-MS/MS analysis using a heat treatment to prevent proteolytic degradation of hormones and remove hemocyanin – a high-molecular weight, highly abundant protein that would otherwise interfere with the analyses of lower-abundance components of the hemolymph. One component of the sample, a 4 kDa peptide, was isolated by reverse-phase chromatography, reduced and alkylated to determine the number of disulfide bonds (three), and was de novo sequenced as the intact peptide and as the trypsinized digest. The sequence mature peptide was found to be modified by C-terminal amidation. Based upon the peptide sequence, this peptide was found to have sequence similarity to defensin antimicrobial peptides from vertebrates. Studies investigating the localization of this peptide to different tissues in H. americanus, and the biological activity of this peptide will be explored.

Characterization of a putative antimicrobial peptide from the hemolymph of the American lobster, Homarus americanus

251st National Meeting (2016)

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