The Department of Biochemistry's weekly BCH 252 seminar series is presented this week by:

Joanna Trylska, Centre of New Technologies, University of Warsaw, Poland 

Seminar Title: "Vitamin B₁₂ as a carrier of modified oligonucleotides to bacterial cells"

Abstract: Short modified oligonucleotides, such as 2’O-methyl RNA and peptide nucleic acid (PNA) that specifically recognize double-stranded DNA or messenger RNA, modulate key biological processes of either transcription or translation. PNA is a synthetic DNA analogue that forms base pairs both with itself and natural nucleic acids. However, both 2’O-methyl RNA and PNA oligomers are not taken up by bacterial cells. For their non-invasive transport carriers are required and efficient ones are yet to be found. We provide experimental evidence that covalent conjugation of vitamin B12 to either PNA or 2’O-methyl RNA makes these oligomers enter E. coli and S. Typhimurium cells.

Vitamin B12 (cobalamin) is an essential enzymatic cofactor either produced or taken up by bacterial cells. The first stage of vitamin B12 uptake to Gram-negative E. coli cells occurs through the outer-membrane receptor protein termed BtuB. After confirming that vitamin B12 transports PNA to E. coli cells through the BtuB receptor, we proceeded to simulate the details of this transport. We built an asymmetric and heterogenous E. coli membrane model around BtuB and applied various enhanced sampling molecular dynamics techniques. We found that indeed transport of the vitamin B12-PNA conjugate is mechanically possible but requires large conformational change of the PNA oligomer. Therefore, as also supported by our experimental evidence, we suggest that vitamin B12—PNA conjugates may be transported through the BtuB protein in the E. coli outer membrane.

Faculty Host: Chia-en Chang; chiaenc@ucr.edu