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Publication Abstract from PubMed

Vitamin B12 (cobalamin) is the most complex B-type vitamin and is synthetized exclusively in a limited number of prokaryotes. Its biologically active variants contain rare organometallic bonds, which are used by enzymes in a variety of central metabolic pathways such as L-methionine synthesis and ribonucleotide reduction. Although its biosynthesis and role as co-factor are well understood, knowledge about uptake of cobalamin by prokaryotic auxotrophs is scarce. Here, we characterize a cobalamin-specific ECF-type ABC transporter from Lactobacillus delbrueckii, ECF-CbrT, and demonstrate that it mediates the specific, ATP-dependent uptake of cobalamin. We solved the crystal structure of ECF-CbrT in an apo conformation to 3.4 A resolution. Comparison with the ECF transporter for folate (ECF-FolT2) from the same organism, reveals how the identical ECF module adjusts to interact with the different substrate binding proteins FolT2 and CbrT. ECF-CbrT is unrelated to the well-characterized B12 transporter BtuCDF, but their biochemical features indicate functional convergence.

Functional and structural characterization of an ECF-type ABC transporter for vitamin B12.,Santos JA, Rempel S, Mous ST, Pereira CT, Ter Beek J, de Gier JW, Guskov A, Slotboom DJ Elife. 2018 May 29;7. pii: 35828. doi: 10.7554/eLife.35828. PMID:29809140^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.