Histone-like protein of Streptomyces lividans

A DNA-binding protein (about 10 kDa and pI>9.7) of Streptomyces lividans TK24 was purified on a denatured DNA-Cellulose column, and then on a native DNA-Cellulose column. The N-terminal amino acid sequence of this protein had high homology with those of small basic DNA-binding proteins known as histone-like proteins. Thus, this protein was designated HSl (histone-like protein of S. lividans). Gel retardation assay revealed that HSl bound with the single-stranded DNA as replication intermediates of pSA1.1. We propose that HSl may participated in the replication of pSA1.1. The hup gene encoding HSl was cloned and sequenced. The deduced N-terminal amino acid sequence, molecular mass (9851 Da) and pI (9.95) were in good agreement with characteristics of HSl. HSl had the signature sequence for the histone-like proteins. Phylogenetic analysis suggested that HSl did not belong to the cluster of histone-like proteins from most of bacteria. The hup transcript of about 500 nucleotides was detected. The hup fragment hybridized with the AseI fragment C in the 9-10 o'clock region of the chromosome. Total DNAs of many Streptomyces species hybridized with the internal region of hup.