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spinqualitylabelsall models 1jcc, resolution 1.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal Structure of a Novel Alanine-Zipper Trimer at 1.7 A Resolution, V13A,L16A,V20A,L23A,V27A,M30A,V34A mutations

Overview

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.

About this Structure

1JCC is a Single protein structure of sequence from Escherichia coli with as ligand. Full crystallographic information is available from OCA.

Reference

Zinc-mediated helix capping in a triple-helical protein., Liu J, Dai J, Lu M, Biochemistry. 2003 May 20;42(19):5657-64. PMID:12741822

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