Cloning and expression of the transglutaminase gene from Streptoverticillium ladakanum in Streptomyces lividans

A gene, tgB1, encoding transglutaminase (TGase) in Streptoverticillium ladakanum B1 was cloned and expressed in Streptomyces lividans. The tgB1 gene consisted of an open reading frame of 1230 nucleotides encoding a protein of 410 amino acids with a calculated molecular weight of 45 780 Da. The deduced amino acid sequence is highly homologous to TGases from Streptoverticillium spp. but exhibits little homology with TGases of Bacillus subtilis and mammalian origins. The putative active site, YGCVG, conserved in Streptoverticillium TGases is also present in TgB1. No −10 and −35 regions of the putative promoter could be identified. Two A+T-rich regions, characteristics of a promoter sequence, were found at bp 238–269 and bp 631–681. The tgB1 gene was expressed in S. lividans JT46 under the control of its endogenous promoter. Immunoblotting of SDS-PAGE revealed that, in addition to protein bands with sizes corresponding to those of the unprocessed and mature TgB1, several bands with sizes in between reacting with anti-TgB1 IgG were present in the culture supernatant of the recombinant strain. This suggests that the recombinant TgB1 was not correctly processed during secretion in the transformed S. lividans JT46. [Copyright &y& Elsevier]