engleski

STRUCTURAL CHARACTERIZATION OF THE STREPTOMYCES COELICOLOR SINGLE-STRANDED DNA-BINDING PROTEIN

In all organisms single-stranded DNA-binding (SSB) proteins sequester and protect singel-stranded DNA intermediates that arise during DNA replication, recombination and repair. All bacterial SSB proteins oligomerize to assemble four copies of a conserved domain called oligonucleotide/oligosaccharide-binding (OB) fold.1 To date, ten crystal structures of 4-OB SSBs have been determined, revealing significant structural variations among them. Recently solved crystal structures of Mycobacterium tuberculosis and Mycobacterium smegmatis SSB have shown a novel quaternary architecture among bacterial SSBs. Unlike other bacterial SSBs, Mycobacterium proteins have one additional β -strand at the C-terminus of OB-fold which is supposed to be responsible for this (?such) quaternary structure. We have crystallised Streptomyces coelicolor SSB protein in space group I222 with unit-cell parameters: a = 100.8, b = 102.1, c = 164.2 Å .2 The structure was solved by molecular replacement method using Mycobacterium smegmatis SSB protein3 pruned of the flexible loops as a search model. Streptomyces coelicolor SSB displays a mycobacterial type of quaternary association. To our knowledge, this is a first known 3D-structure of SSBs from Streptomyces. A detailed structural comparison between mycobacterial and streptomyces SSBs will be discussed.

SSB

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