PUBLICATION

Functional and phylogenetic characterization of non-canonical vitamin B12-binding proteins in zebrafish suggests involvement in cobalamin transport.

Authors
Benoit, C.R., Stanton, A.E., Tartanian, A.C., Motzer, A.R., McGaughey, D.M., Bond, S.R., Brody, L.C.
ID
ZDB-PUB-180922-3
Date
2018
Source
The Journal of biological chemistry   293(45): 17606-17621 (Journal)
Registered Authors
Keywords
affinity, cobalamin, one-carbon metabolism, phylogenetics, protein evolution, transcobalamin, transport, vitamin B12, zebrafish
MeSH Terms
  • Animals
  • CRISPR-Cas Systems
  • Protein Domains
  • Transcobalamins*/chemistry
  • Transcobalamins*/genetics
  • Transcobalamins*/metabolism
  • Vitamin B 12/chemistry
  • Vitamin B 12/genetics
  • Vitamin B 12/metabolism
  • Zebrafish*/genetics
  • Zebrafish*/metabolism
  • Zebrafish Proteins/chemistry
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism
PubMed
30237171 Full text @ J. Biol. Chem.
Citation
Benoit, C.R., Stanton, A.E., Tartanian, A.C., Motzer, A.R., McGaughey, D.M., Bond, S.R., Brody, L.C. (2018) Functional and phylogenetic characterization of non-canonical vitamin B12-binding proteins in zebrafish suggests involvement in cobalamin transport.. The Journal of biological chemistry. 293(45):17606-17621.
Abstract
In humans, transport of food-derived cobalamin (vitamin B12) from the digestive system into the bloodstream involves three paralogous proteins: transcobalamin (TC), haptocorrin (HC), and intrinsic factor (IF). Each of these proteins contains two domains, an α-domain and a β-domain, which together form a cleft in which cobalamin binds. Zebrafish (Danio rerio) are thought to possess only a single cobalamin transport protein, referred to as Tcn2, which is a transcobalamin homolog. Here, we used CRISPR/Cas9 mutagenesis to create null alleles of tcn2 in zebrafish. Fish homozygous for tcn2-null alleles were viable and exhibited no obvious developmentally- or behaviorally-abnormal phenotypes. For this reason, we hypothesized that previously unidentified cobalamin carrier proteins encoded in the zebrafish genome may provide an additional pathway for cobalamin transport. We identified genes predicted to code for two such proteins, Tcn-beta-a (Tcnba) and Tcn-beta-b (Tcnbb), which differ from all previously characterized cobalamin transport proteins as they lack the α-domain. These β-domain-only proteins are representative of an undescribed class of cobalamin-carrier proteins that are highly conserved throughout the ray-finned fishes. We observed that the genes encoding the three cobalamin transport homologs, tcn2, tcnba, and tcnbb, are expressed in unique spatial and temporal patterns in the developing zebrafish. Moreover, exogenously-expressed recombinant Tcnba and Tcnbb bound cobalamin with high affinity, comparable to binding by full-length Tcn2. Taken together, our results suggest that this noncanonical protein structure has evolved to fully function as a cobalamin-carrier protein, thereby allowing for a compensatory cobalamin transport mechanism in the tcn2-/- zebrafish.
Genes / Markers
Figures
Show all Figures
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Antibodies
Orthology
Engineered Foreign Genes
Mapping
Your Input Welcome
We welcome your input and comments. Please use this form to recommend updates to the information in ZFIN. We appreciate as much detail as possible and references as appropriate. We will review your comments promptly.
Please check the highlighted fields and try again.
Thank you for submitting comments. Your input has been emailed to ZFIN curators who may contact you if additional information is required.
Oops. Something went wrong. Please try again later.