1smn
From Proteopedia
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IDENTIFICATION OF THE SERRATIA ENDONUCLEASE DIMER: STRUCTURAL BASIS AND IMPLICATIONS FOR CATALYSIS
Overview
The Serratia endonuclease is an extracellularly secreted enzyme capable of, cleaving both single- and double-stranded forms of DNA and RNA. It is the, first member of a large class of related and usually dimeric endonucleases, for which a structure is known. Using X-ray crystallography, the structure, of monomer of this enzyme was reported by us previously (Miller MD et al., 1994, Nature Struct Biol 1:461-468). We now confirm the dimeric nature of, this enzyme through light-scattering experiments and identify the, physiologic dimer interface through crystal packing analysis. This, dimerization occurs through an isologous twofold interaction localized to, the carboxy-terminal subdomain of the enzyme. The dimer is a prolate, ellipsoid with dimensions 30 A x 35 A x 90 A. The dimer interface is flat, and contains four salt links, several hydrogen bonds, and nonpolar, interactions. Buried water is prominent in this interface and it includes, an unusual "cubic" water cluster. The position of the two active sites in, the dimer suggests that they can act independently in their cleavage of, DNA, but have a geometrical advantage in attacking substrate relative to, the monomer.
About this Structure
1SMN is a Single protein structure of sequence from Serratia marcescens. Active as Serratia marcescens nuclease, with EC number 3.1.30.2 Full crystallographic information is available from OCA.
Reference
Identification of the Serratia endonuclease dimer: structural basis and implications for catalysis., Miller MD, Krause KL, Protein Sci. 1996 Jan;5(1):24-33. PMID:8771193
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