title: Structure of the unbound form of HIV-1 subtype A protease: comparison with unbound forms of proteases from other HIV subtypes.
abstract: The crystal structure of the unbound form of HIV-1 subtype A protease (PR) has been determined to 1.7 A resolution and refined as a homodimer in the hexagonal space group P6(1) to an R(cryst) of 20.5%. The structure is similar in overall shape and fold to the previously determined subtype B, C and F PRs. The major differences lie in the conformation of the flap region. The flaps in the crystal structures of the unbound subtype B and C PRs, which were crystallized in tetragonal space groups, are either semi-open or wide open. In the present structure of subtype A PR the flaps are found in the closed position, a conformation that would be more anticipated in the structure of HIV protease complexed with an inhibitor. The amino-acid differences between the subtypes and their respective crystal space groups are discussed in terms of the differences in the flap conformations.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA.
authors.forename: Arthur H
authors.initials: AH
authors.lastname: Robbins
authors.forename: Roxana M
authors.initials: RM
authors.lastname: Coman
authors.forename: Edith
authors.initials: E
authors.lastname: Bracho-Sanchez
authors.forename: Marty A
authors.initials: MA
authors.lastname: Fernandez
authors.forename: C Taylor
authors.initials: CT
authors.lastname: Gilliland
authors.forename: Mi
authors.initials: M
authors.lastname: Li
authors.forename: Mavis
authors.initials: M
authors.lastname: Agbandje-McKenna
authors.forename: Alexander
authors.initials: A
authors.lastname: Wlodawer
authors.forename: Ben M
authors.initials: BM
authors.lastname: Dunn
authors.forename: Robert
authors.initials: R
authors.lastname: McKenna
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D016333:HIV Protease / Q000737:chemistry* / Q000378:metabolism; D015497:HIV-1 / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D016333:HIV Protease