1H, 13C, and 15N resonance assignments of the amyloidogenic peptide SEM2(49–107) by NMR spectroscopy

It has been shown that human seminal fluid is a major factor in enhancing HIV activity. The SEM2(49–107) peptide is a product of cleavage after ejaculation by internal prostheses of the semenogelin 2 protein, expressed in seminal vesicles. It is established that the peptide SEM2(49–107) forms amyloid fibrils, which increase probability of contracting HIV infection. In this nuclear magnetic resonance (NMR) study, we present almost complete (86%) resonance assignments for the ¹H ¹⁵N and ¹³C atoms of the backbone and side-chain of the SEM2(49–107) peptide (BioMagResBank accession number 52356). The secondary structure of SEM2(49–107) peptide was estimated by using two approaches, secondary chemical shifts analysis (CSI) and TALOS-N prediction. Analysis of the secondary structure of the SEM2(49–107) peptide using both methods revealed that the peptide contains helical segments at the C-terminus. Also in this work, we used phase-sensitive 2D HSQC ¹H- ¹⁵N experiments measuring longitudinal T₁ and transverse T₂ NMR relaxation times to report predicted secondary structure and backbone dynamics of the SEM2(49–107) peptide. This resonance assignment will form the basis of future NMR research, contributing to a better understanding of the peptide structure and internal dynamics of the molecule.