The mobility of an HIV-1 integrase active site loop is correlated with catalytic activity.

Important note: Information in this article was accurate in 1999. The state of the art may have changed since the publication date.

The mobility of an HIV-1 integrase active site loop is correlated with catalytic activity.

Biochemistry. 1999 Jul 13;38(28):8892-8. Unique Identifier : AIDSLINE PDB/1B92
Greenwald J; Le V; Butler SL; Bushman FD; Choe S; Structural Biology Laboratory, The Salk Institute, La Jolla,; California 92037, USA.

Abstract: Replication of HIV-1 requires the covalent integration of the viral cDNA into the host chromosomal DNA directed by the virus-encoded integrase protein. Here we explore the importance of a protein surface loop near the integrase active site using protein engineering and X-ray crystallography. We have redetermined the structure of the integrase catalytic domain (residues 50-212) using an independent phase set at 1.7 A resolution. The structure extends helix alpha4 on its N-terminal side (residues 149-154), thus defining the position of the three conserved active site residues. Evident in this and in previous structures is a conformationally flexible loop composed of residues 141-148. To probe the role of flexibility in this loop, we replaced Gly 140 and Gly 149, residues that appear to act as conformational hinges, with Ala residues. X-ray structures of the catalytic domain mutants G149A and G140A/G149A show further rigidity of alpha4 and the adjoining loop. Activity assays in vitro revealed that these mutants are impaired in catalysis. The DNA binding affinity, however, is minimally affected by these mutants as assayed by UV cross-linking. We propose that the conformational flexibility of this active site loop is important for a postbinding catalytic step.

Keywords: JOURNAL ARTICLE Alanine/GENETICS Binding Sites/GENETICS Catalysis Computer Simulation Crystallography, X-Ray DNA/METABOLISM Glycine/GENETICS HIV Integrase/*CHEMISTRY/GENETICS/*METABOLISM Models, Molecular Mutagenesis, Site-Directed Peptide Fragments/*CHEMISTRY/GENETICS/*METABOLISM Protein Conformation Protein Folding Support, Non-U.S. Gov't Support, U.S. Gov't, P.H.S.
991030
A99A0969

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