[Cobalamins and tRNA methyltransferase activity in E. coli cells]

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Cobalamins, including methylcobalamin (MeCbl) and cyanocobalamin (CNCbl), are vital B12 vitamers.
• E. coli utilizes cobalamins for essential metabolic processes, including methylation reactions.

Purpose of the Study:

• To investigate the impact of methylcobalamin (MeCbl) versus cyanocobalamin (CNCbl) on E. coli growth dynamics.
• To analyze the effects of MeCbl on methyl group transfer and tRNA methylation in E. coli.

Main Methods:

• Culturing E. coli 113-3 in mineral media supplemented with either MeCbl or CNCbl.
• Fractionation of cell-free extracts using Sephadex-DEAE cellulose chromatography.
• Assessing methyl group (14CH3) transfer from S-adenosylmethionine (Adomet) to submethylated tRNA.
• Chromatographic analysis of tRNA methylated bases.

Main Results:

• E. coli growth with MeCbl reached the end of the logarithmic phase 60 minutes earlier than with CNCbl.
• Cell-free extracts from MeCbl-grown cells exhibited quantitative and qualitative differences in protein fractions.
• Protein fractions from MeCbl-grown cells showed a 1.5-3 fold increase in methyl group transfer to tRNA.
• Incorporation of methyl groups into m7G was 50% higher in cells grown with MeCbl.

Conclusions:

• Methylcobalamin significantly enhances E. coli growth rate and methyl group metabolism compared to cyanocobalamin.
• MeCbl promotes more efficient methyl group transfer to tRNA, particularly impacting m7G methylation.
• These findings highlight the distinct roles of different cobalamin forms in bacterial physiology.