title: A conformational analysis of Walker motif A [GXXXXGKT (S)] in nucleotide-binding and other proteins.
abstract: The sequence GXXXXGKT/S, popularly known as Walker motif A, is widely believed to be the site for binding nucleotides in many proteins. Examination of the crystal structures in the Protein Data Bank showed that about half of the examples having these sequences do not bind or use nucleotides. Data analyses showed 92 different Walker sequences of the variable quartet (XXXX). Ramachandran angles in this segment revealed conformational similarity in the group of 45 proteins, known to bind or utilize nucleotides. The conformations of this segment in other proteins differ widely and it is not known whether they play any role in their functions. A flip of a peptide unit at different locations, with little change in the backbone conformation was noted in nine pairs of these proteins having same Walker sequence. An examination of the immediate neighborhood of the Walker sequence indicates that this region is preceded by a beta-strand and followed by an alpha-helix, resulting in the motif beta-W-alpha, an invariant feature amongst nucleotide-binding proteins.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India. ramki@crmbu2.iisc.ernet.in
authors.forename: C
authors.initials: C
authors.lastname: Ramakrishnan
authors.forename: V S
authors.initials: VS
authors.lastname: Dani
authors.forename: T
authors.initials: T
authors.lastname: Ramasarma
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019295:Computational Biology / Q000379:methods*; D016384:Consensus Sequence; D030562:Databases, Protein; D006801:Humans; D008958:Models, Molecular; D009711:Nucleotides / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D009711:Nucleotides; D011506:Proteins