Rhodobacterales use a unique L-threonine kinase for the assembly of the nucleotide loop of coenzyme B 12

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

Abstract

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 2.7.1.177) 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

Substances

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