Membrane transport of cobalamin

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Abstract

A wide variety of organisms encode cobalamin-dependent enzymes catalyzing essential metabolic reactions, but the cofactor cobalamin (vitamin B12) is only synthesized by a subset of bacteria and archaea. The biosynthesis of cobalamin is complex and energetically costly, making cobalamin variants and precursors metabolically valuable. Auxotrophs for these molecules have evolved uptake mechanisms to compensate for the lack of a synthesis pathway. Bacterial transport of cobalamin involves the passage over one or two lipidic membranes in Gram-positive and -negative bacteria, respectively. In higher eukaryotes, a complex system of carriers, receptors and transporters facilitates the delivery of the essential molecule to the tissues. Biochemical and genetic approaches have identified different transporter families involved in cobalamin transport. The majority of the characterized cobalamin transporters are active transport systems that belong to the ATP-binding cassette (ABC) superfamily of transporters. In this chapter, we describe the different cobalamin transport systems characterized to date that are present in bacteria and humans, as well as yet-to-be-identified transporters.

Original languageEnglish
Title of host publicationVitamins and Hormones
EditorsGerald Litwack
PublisherACADEMIC PRESS INC ELSEVIER SCIENCE
Chapter5
Pages121-148
Number of pages28
DOIs
Publication statusPublished - 22-Mar-2022

Publication series

NameVitamins and Hormones
PublisherElsevier
Volume119
ISSN (Print)0083-6729

Keywords

  • ABC transporter
  • Cobalamin uptake
  • Mechanisms of membrane transport
  • Membrane protein
  • Membrane transport
  • Protein structure
  • Vitamin B12 uptake

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