Structural characterization of semen coagulum-derived SEM1(86-107) amyloid fibrils that enhance HIV-1 infection

Biochemistry. 2014 May 27;53(20):3267-77. doi: 10.1021/bi500427r. Epub 2014 May 12.


SEM1(86-107) is a 22-residue peptide corresponding to residues 86-107 in the semenogelin I protein. SEM1(86-107) is an abundant component of freshly liquefied semen and forms amyloid fibrils capable of enhancing HIV infection. To probe the factors affecting fibril formation and gain a better understanding of how differences in pH between semen and vaginal fluid affect fibril stability, this study determined the effect of pH on SEM1(86-107) fibril formation and dissociation. The SEM1(86-107) fibril structure (i.e., residues that comprise the fibrillar core) was also probed using hydrogen-deuterium exchange mass spectrometry (HDXMS) and hydroxyl radical-mediated protein modification. The average percent exposure to hydroxyl radical-mediated modification in the SEM1(86-107) fibrils was determined without requiring tandem mass spectrometry spectral acquisition or complete separation of modified peptides. It was found that the residue exposures calculated from HDXMS and hydroxyl radical-mediated modification were similar. These techniques demonstrated that three regions of SEM1(86-107) comprise the amyloid fibril core and that positively charged residues are exposed, suggesting that electrostatic interactions between SEM1(86-107) and HIV or the cell surface may be responsible for mediating HIV infection enhancement by the SEM1(86-107) fibrils.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Amyloid / chemistry
  • Amyloid / genetics
  • HIV Infections / genetics
  • HIV Infections / metabolism*
  • HIV-1*
  • Humans
  • Male
  • Molecular Sequence Data
  • Semen / chemistry*
  • Semen / physiology*
  • Seminal Vesicle Secretory Proteins / chemistry*
  • Seminal Vesicle Secretory Proteins / genetics*


  • Amyloid
  • Seminal Vesicle Secretory Proteins
  • seminal vesicle-specific antigen