Gene Inactivation Study on gntK, a Putative C-methyltransferase Gene in Gentamicin Biosynthesis from Micromonospora echinospora

GntK harbors methyltransferase-related cobalamin-binding domain and radical S-adenosylmethionine domain. The gntK-inactivation mutant of Micromonospora echinospora accumulated higher levels of gentamicin Cla and lower levels of gentamicin C1 and C2 isomers compared to the wild-type strain. Based on these results, we propose that GntK is involved in C-methylation on C-6′ in gentamicin X2 but is dispensable in gentamicin biosynthesis.