The Structure of Fibril-Forming SEM1(86-107) Peptide Increasing the HIV Infectivity

SEM1(86-107) peptide is a cleavage product of semenogelin 1 (SEM1) expressed in seminal vesicles. SEM1(86-107) forms amyloid fibrils in semen increasing HIV infectivity by up to 3-5 orders of magnitude. The study of fibrillation process includes peptide spatial structure determination. This paper presents the information about the SEM1(86-107) structure obtained by the Nuclear Magnetic Resonance (NMR) spectroscopy and Circular Dichroism (CD) spectroscopy. Assignment of hydrogen chemical shifts and internuclear distances of the SEM1(86-107) with following prediction of secondary structure was carried out by the NMR spectroscopy. Also the spatial structure was calculated using the XPLOR-NIH software. The spatial structure analysis has shown the containing the regions with the random coil conformations in the SEM1(86-107) peptide. Analysis of the structure ensemble showed containing fragments with high convergence: Leu87-Lys92, Thr94-Gln97, and Gln104-Leu107. It can be assumed that these fragments are responsible for the fibrillation process via low their mobility. CD spectroscopy was applied to determine the secondary structure of SEM1(86-107). CD measurement confirmed that the prevailing secondary structure content of SEM1(86-107) peptide is a random coil.

Automated summary

SEM1(86-107) peptide is a cleavage product expressed in seminal vesicles, forming amyloid fibrils in semen and potentially increasing HIV infectivity. The spatial structure of SEM1(86-107) was studied using NMR and CD spectroscopy, revealing regions with random coil conformations. Analysis showed that specific fragments within the peptide are responsible for the fibrillation process.