A gene, nagA. encoding transglutaminase (TGase) in Streptomyces platensis M5218 was cloned and expressed in Streptomyces lividans. The mtgA gene consisted of an open reading frame of 1254 nucleotides encoding a protein of 418 amino acids with a calculated molecular weight of 46,511 Da. The deduced an-Lino acid sequence shows 69.3-77.7% identity to TGases from Streptoverticillium spp., but exhibits less than 35% identity with TGases of Bacillus subtilis and eukaryotic origins. The putative active site, YGCVG, conserved in Streptoverticillium TGases is also present in MtgA. SDS-PAGE and immunoblotting analyses revealed that an intensively stained protein band with a size corresponding to that of mature TGase was present in the culture supernatant of the recombinant strain. The result suggests that the recombinant MtgA may be highly expressed and correctly processed during secretion in the transformed S. lividans JT46. (c) 2005 Elsevier Ltd. All rights reserved.