1zde

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spinqualitylabelsall models 1zde, resolution 1.95Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

1.95 Angstrom Crystal Structure of a dnaE Intein Precursor from Synechocystis Sp. Pcc 6803

Overview

The first naturally occurring split intein was found in the dnaE gene of, Synechocystis sp. PCC6803 and belongs to a subclass of inteins without a, penultimate histidine residue. We describe two high-resolution crystal, structures, one derived from an excised Ssp DnaE intein and the second, from a splicing-deficient precursor protein. The X-ray structures indicate, that His147 in the conserved block F activates the side-chain N(delta), atom of the intein C-terminal Asn159, leading to a nucleophilic attack on, the peptide bond carbonyl carbon atom at the C-terminal splice site. In, this process, Arg73 appears to stabilize the transition state by, interacting with the carbonyl oxygen atom of the scissile bond. Arg73 also, seems to substitute for the conserved penultimate histidine residue in the, formation of an oxyanion hole, as previously identified in other inteins., The finding that the precursor structure contains a zinc ion chelating the, highly conserved Cys160 and Asp140 reveals the structural basis of, Zn2+-mediated inhibition of protein splicing. Furthermore, it is of, interest to observe that the carbonyl carbon atom of Asn159 and N(eta) of, Arg73 are 2.6 angstroms apart in the free intein structure and 10.6, angstroms apart in the precursor structure. The orientation change of the, aromatic ring of Tyr-1 following the initial acyl shift may be a key, switching event contributing to the alignment of Arg73 and the C-terminal, scissile bond, and may explain the sequential reaction property of the Ssp, DnaE intein.

About this Structure

1ZDE is a Single protein structure of sequence from Synechocystis sp. with ZN and CA as ligands. Active as DNA-directed DNA polymerase, with EC number 2.7.7.7 Full crystallographic information is available from OCA.

Reference

Crystal structures of an intein from the split dnaE gene of Synechocystis sp. PCC6803 reveal the catalytic model without the penultimate histidine and the mechanism of zinc ion inhibition of protein splicing., Sun P, Ye S, Ferrandon S, Evans TC, Xu MQ, Rao Z, J Mol Biol. 2005 Nov 11;353(5):1093-105. Epub 2005 Sep 30. PMID:16219320

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