title: Analysis of the mechanical properties of wild type and hyperstable mutants of the HIV-1 capsid.
abstract: BACKGROUND
  The human immunodeficiency virus (HIV-1) capsid is a self-assembled protein shell that contains the viral genome. During the stages between viral entry into a host cell and nuclear import of the viral DNA, the capsid dissociates in a process known as uncoating, which leads to the release of the viral genetic material. Mutations that alter the stability of the capsid affect the uncoating rate and impair HIV-1 infectivity.
  
  
  RESULTS
  To gain further insight into the role of capsid stability during uncoating, we used atomic force spectroscopy to quantify the stiffness of the capsid. Empty in vitro assemblies of wild type (WT) and mutant recombinant HIV-1 capsid protein (CA) as well as isolated WT and mutant HIV-1 cores (i.e., filled capsids) were analyzed. We find that hyperstable CA mutant assemblies (A204C, A14C/E45C, E45A and E45A/R132T) are significantly stiffer than WT assemblies. However, the hardening effect of disulfide crosslinking (A204C and A14C/E45C) is lower than that of hydrophobic interactions (E45A and E45A/R132T).
  
  
  CONCLUSIONS
  Our results demonstrate that mutations that increase the intrinsic stability of the HIV-1 capsid have an increased stiffness of their lattice.
authors.affiliation: Department of Physiology and Cell Biology, Ben-Gurion University of the Negev, 84105, Beer-Sheva, Israel.
authors.forename: Ruben
authors.initials: R
authors.lastname: Ramalho
authors.affiliation: Department of Physiology and Cell Biology, Ben-Gurion University of the Negev, 84105, Beer-Sheva, Israel.
authors.forename: Sanela
authors.initials: S
authors.lastname: Rankovic
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Aiken
authors.affiliation: Department of Physiology and Cell Biology, Ben-Gurion University of the Negev, 84105, Beer-Sheva, Israel. roussoi@bgu.ac.il.
authors.forename: Itay
authors.initials: I
authors.lastname: Rousso
mesh_terms: D002213:Capsid / Q000737:chemistry*; D055598:Chemical Phenomena; D016655:HIV Core Protein p24 / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000737:chemistry* / Q000235:genetics; D018625:Microscopy, Atomic Force; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D016655:HIV Core Protein p24; D050505:Mutant Proteins
keywords: Atomic force microscopy; Capsid; HIV; Stiffness