Rhodobacterales use a unique L-threonine kinase for the assembly of the nucleotide loop of coenzyme B12

Mol Microbiol. 2018 Oct;110(2):239-261. doi: 10.1111/mmi.14100. Epub 2018 Oct 3.


Several of the enzymes involved in the conversion of adenosylcobyric acid (AdoCby) to adenosylcobamide (AdoCba) are yet to be identified and characterized in some cobamide (Cba)-producing prokaryotes. Using a bioinformatics approach, we identified the bluE gene (locus tag RSP_0788) of Rhodobacter sphaeroides 2.4.1 as a putative functional homolog of the L-threonine kinase enzyme (PduX, EC of S. enterica. In AdoCba, (R)-1-aminopropan-2-ol O-phosphate (AP-P) links the nucleotide loop to the corrin ring; most known AdoCba producers derive AP-P from L-Thr-O-3-phosphate (L-Thr-P). Here, we show that RsBluE has L-Thr-independent ATPase activity in vivo and in vitro. We used 31 P-NMR spectroscopy to show that RsBluE generates L-Thr-P at the expense of ATP and is unable to use L-Ser as a substrate. BluE from R. sphaeroides or Rhodobacter capsulatus restored AdoCba biosynthesis in S. enterica ΕpduX and R. sphaeroides ΕbluE mutant strains. R. sphaeroides ΕbluE strains exhibited a decreased pigment phenotype that was restored by complementation with BluE. Finally, phylogenetic analyses revealed that bluE was restricted to the genomes of a few Rhodobacterales that appear to have a preference for a specific form of Cba, namely Coᴽ-(ᴽ-5,6-dimethylbenzimidazolyl-Coᵦ-adenosylcobamide (a.k.a. adenosylcobalamin, AdoCbl; coenzyme B12 , CoB12 ).

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Cobalt / metabolism
  • Cobamides / metabolism*
  • Nucleotides / metabolism*
  • Phylogeny
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Rhodobacter capsulatus / enzymology*
  • Rhodobacter capsulatus / genetics
  • Rhodobacter sphaeroides / enzymology*
  • Rhodobacter sphaeroides / genetics
  • Salmonella enterica / enzymology
  • Salmonella enterica / genetics
  • Serine / metabolism
  • Threonine / metabolism


  • Bacterial Proteins
  • Cobamides
  • Nucleotides
  • Threonine
  • Cobalt
  • Serine
  • Protein Serine-Threonine Kinases