earticle

영어

The small coenzyme Biotin (vitamin H) functions as a cofactor that aids in the transfer of CO2 groups to various target macromolecules. A modification of biotin carboxylase (BC) or alpha subunit of acyl-CoA carboxylase (ACCase) via biotin attachment regulates the catabolic enzyme activity at the posttranslational level. The biotinylation of apo-BC to holo-BC is conducted by biotin apo-protein ligase (BPL) via utilization of a molecule ATP. The identified in Streptomyces toxytricini chromosome stbpl gene encodes a 29,870 (31,320) Da protein (StBpl) showing 20% identity with Escherichia coli BirA (EcBirA) protein. the StBpl showed very low homology with the N-terminal sequence of EcBirA, DNA binding motif involved in transcriptional regulation of bio operon. The protein is also smaller than EcBirA with 15-30 amino acid residues. In this report we cloned, overexpressed and biochemically characterized the StBpl protein from S. toxytricini. accA1 gene identified in a different DNA region of the S. toxytricini genome encodes 70 kDa protein (StAccA1), an biotin carboxylase of ACCase gene involved in primary (fatty acids) metabolism. The apo-StAccA1 or apo-BC recombinant protein was also expressed, purified and used as a substrate for biotinylation assay in vitro by StBpl and/or in vivo by the host EcBirA.