Zinc-Mediated Helix Capping in A Triple-Helical ProteinLiu, J., Dai, J., Lu, M.
(2003) Biochemistry 42: 5657-5664
- PubMed: 12741822
- DOI: 10.1021/bi026828a
- PubMed Abstract:
Specific sequence signals at alpha-helix termini can assist protein folding by punctuating and cueing secondary structural elements in the final native conformation. Here we report the crystallization of a 56-residue alanine-containing peptide, denot ...
Specific sequence signals at alpha-helix termini can assist protein folding by punctuating and cueing secondary structural elements in the final native conformation. Here we report the crystallization of a 56-residue alanine-containing peptide, denoted Ala-10(56), in the presence of Zn(2+). The 1.7 A crystal structure shows that Ala-10(56) forms a parallel trimeric coiled coil with three zinc ions anchoring distinct capping conformations at the amino-terminal ends of the three helices. In each polypeptide chain, the free alpha-amino nitrogen and carbonyl oxygen of the amino-terminal Ser residue coordinate to a Zn(2+) ion to form a five-membered chelate, and the syn-unidentate interaction of the Asp7 side chain with the Zn(2+) cation leads to the formation of a unique docking arrangement for helix capping. Moreover, the coordination of the zinc ion involves a neighboring trimer molecule in the crystal. Consequently, the crystal contacts are stabilized by carboxylate-Zn(2+) interactions between four Ala-10(56) trimers in the crystal lattice. The observed synergy between the protein-zinc ion recognition and the helix-packing arrangements would contribute to the conformational specificity of the Ala-10(56) trimer.
Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10021, USA.