In vitro activity comparison of Erm proteins from Firmicutes and Actinobacteria
2016
Jin, H.J., The University of Suwon, Kyunggi-Do, Republic of Korea
Erm proteins methylate the specific adenine residue (A2058, E. coli numbering) on 23S rRNA to confer the MLSB (macrolidelincosamide- streptogramin B) antibiotic resistance on a variety of microorganisms ranging from antibiotic producers to pathogens. When phylogenetic tree is constructed, two main clusters come out forming each cluster of Actinobacteria and Firmicutes. Two representative Erm proteins from each cluster were selected and their in vitro methylation activities were compared. ErmS and ErmE from Actinobacteria cluster exhibited much higher activities than ErmB and ErmC′ from Firmicutes: 9 fold difference when ErmC′ and ErmE were compared and 13 fold between ErmS and ErmB. Most of the difference was observed and presumed to be caused by N-terminal and C-terminal extra region from ErmS and ErmE, respectively because NT59TE in which N-terminal end 59 amino acids was truncated from wild type ErmS exhibited only 22.5% of wild type ErmS activity. Meanwhile, even NT59TE showed three and 2.2 times more activity when it was compared to ErmB and C, respectively, suggesting core region from antibiotic producers contains extra structure enabling higher activity. This is suggested to be possible through the extra region of 197RWS199 (from both ErmS and ErmE), 261GVGGSLY267 (from ErmS), and 261GVGGNIQ267 (from ErmE) and 291SVV293 (from ErmS) and 291GAV293 (from ErmE) by multiple sequence alignment.
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