DNA binding protein of mycobacteria and human immune response.

A dual step procedure was used to identify a 30 kDa DNA binding protein of mycobacteria (HLPMt) which is a target of human T and B cell response. The immunodominance of HLPMt was estabished by T cell blot assay as well as by subtractive immunoblot assay. This protein is not secreted into the extracellular culture fluid and is different from the 85 ABC complex of proteins as seen by immunoblots and ELISA. The protein is capable of inducingin vitro lymphoproliferation in tuberculin reactors. The protein was purified for the generation of monospecific sera and for amino acid sequencing. The sequence of the 16 amino acid long peptide derived from the 30 kDa protein showed a 100% homology with the translated sequence of a cosmid cY349 (Sanger Centre, Cambridge, UK). The ORF was predicted to code for a protein of 214 amino acids. Oligonucleotide primers were designed against the 5' and 3' end of the gene and the gene was PCR amplified, cloned and expressed inE.coli. The protein has unique dual domains which show homology to both bacterial HU proteins and to eukaryotic histones H1.