Single-stranded DNA-binding proteins (SSBs) play a crucial role in DNA processing such as
replication, repair and recombination in all organisms, from bacteria to human. Streptomyces
coelicolor ssb gene was overexpressed in a heterologous host, Escherichia coli NM522. 15 mg
of purified protein from 1 dm3 of culture was obtained in one-step procedure applying Ni2+
chelating chromatography. Among bacterial SSBs with the solved crystal structure, the S.
coelicolor SSB displayed significant sequence similarity with those from Mycobacterium
tuberculosis and Mycobacterium smegmatis, slow growing bacteria with a high GC content.
Moreover, conserved amino acid region that forms additional ß strand in mycobacterial SSBs
was also found in S. coelicolor SSB. The full-length protein readily crystallises in space group
I222 or I212121 with unit-cell parameters a = 100.8, b = 102.1, c = 164.2 Å. The asymmetric
unit is expected to contain four monomers with solvent content of 52–55 %
