title: Crystal structure of the third KH domain of human poly(C)-binding protein-2 in complex with a C-rich strand of human telomeric DNA at 1.6 A resolution.
abstract: KH (hnRNP K homology) domains, consisting of approximately 70 amino acid residues, are present in a variety of nucleic-acid-binding proteins. Among these are poly(C)-binding proteins (PCBPs), which are important regulators of mRNA stability and posttranscriptional regulation in general. All PCBPs contain three different KH domains and recognize poly(C)-sequences with high affinity and specificity. To reveal the molecular basis of poly(C)-sequence recognition, we have determined the crystal structure, at 1.6 A resolution, of PCBP2 KH3 domain in complex with a 7-nt DNA sequence (5'-AACCCTA-3') corresponding to one repeat of the C-rich strand of human telomeric DNA. The domain assumes a type-I KH fold in a betaalphaalphabetabetaalpha configuration. The protein-DNA interface could be studied in unprecedented detail and is made up of a series of direct and water-mediated hydrogen bonds between the protein and the DNA, revealing an especially dense network involving several structural water molecules for the last 2 nt in the core recognition sequence. Unlike published KH domain structures, the protein crystallizes without protein-protein contacts, yielding new insights into the dimerization properties of different KH domains. A nucleotide platform, an interesting feature found in some RNA molecules, was identified, evidently for the first time in DNA.
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143-2280, USA.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Fenn
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Du
authors.forename: John K
authors.initials: JK
authors.lastname: Lee
authors.forename: Richard
authors.initials: R
authors.lastname: Tjhen
authors.forename: Robert M
authors.initials: RM
authors.lastname: Stroud
authors.forename: Thomas L
authors.initials: TL
authors.lastname: James
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry*; D016415:Sequence Alignment; D016615:Telomere / Q000737:chemistry*
chemical_list: C501903:PCBP2 protein, human; D016601:RNA-Binding Proteins; D004247:DNA