title: Active-site mobility in human immunodeficiency virus, type 1, protease as demonstrated by crystal structure of A28S mutant.
abstract: The mutation Ala28 to serine in human immunodeficiency virus, type 1, (HIV-1) protease introduces putative hydrogen bonds to each active-site carboxyl group. These hydrogen bonds are ubiquitous in pepsin-like eukaryotic aspartic proteases. In order to understand the significance of this difference between HIV-1 protease and homologous, eukaryotic aspartic proteases, we solved the three-dimensional structure of A28S mutant HIV-1 protease in complex with a peptidic inhibitor U-89360E. The structure has been determined to 2.0 A resolution with an R factor of 0.194. Comparison of the mutant enzyme structure with that of the wild-type HIV-1 protease bound to the same inhibitor (Hong L, Treharne A, Hartsuck JA, Foundling S, Tang J, 1996, Biochemistry 35:10627-10633) revealed double occupancy for the Ser28 hydroxyl group, which forms a hydrogen bond either to one of the oxygen atoms of the active-site carboxyl or to the carbonyl oxygen of Asp30. We also observed marked changes in orientation of the Asp25 catalytic carboxyl groups, presumably caused by the new hydrogen bonds. These observations suggest that catalytic aspartyl groups of HIV-1 protease have significant conformational flexibility unseen in eukaryotic aspartic proteases. This difference may provide an explanation for some unique catalytic properties of HIV-1 protease.
authors.affiliation: Protein Studies, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City 73104, USA.
authors.forename: L
authors.initials: L
authors.lastname: Hong
authors.forename: J A
authors.initials: JA
authors.lastname: Hartsuck
authors.forename: S
authors.initials: S
authors.lastname: Foundling
authors.forename: J
authors.initials: J
authors.lastname: Ermolieff
authors.forename: J
authors.initials: J
authors.lastname: Tang
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D016333:HIV Protease / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000201:enzymology*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D016333:HIV Protease