Solid-phase synthesis and solution conformation of two overlapping fragments of SPFE peptide using 2D-NMR

Abstract

Study of amino acid mutation effects on the structure, dynamics and function of peptides/proteins is of considerable prominence. Seminalplasmin (SPLN) is a 47-residue peptide isolated from bovine seminal plasma and has broad spectrum antimicrobial activity, without any hemolytic activity. The 28-40 segment of SPLN with the sequence PKLLETFLSKWIG, designated as SPF, is the most hydrophobic stretch of SPLN with helical structure and primarily responsible for the membrane-perturbing activity of SPLN. An analogue of SPF peptide with K2E and K10E substitutions, designated as SPFE, is lacking helical structure and hence antimicrobial activity. We have synthesized, by solid phase method, and solved the conformation, by NMR spectroscopic method, of two overlapping fragments of SPFE with the sequences PELLETFL (1- 8 fragment) and FLSEWIG (7-13 fragment) under hydrophobic environment (DMSO-<em>d</em>₆). Results show that the lysine residues at positions 2 and 10 are very crucial for the helical structure and hence the biological activity of SPF peptide. The experimental results are in harmony with the formerly testified molecular dynamic simulation studies.