Table 2.

CN-Cbl utilization phenotype of cysteine substitutions in the BtuB Ton box and effect of the L8P and V10P substitutionsa

btuBallelebCN-Cbl concn (nM) for maximal growth of a strain carrying BtuB with the indicated substitutionc
AloneL8PV10P
WT0.5>5,000>5,000
D6C0.55500
T7C0.50.5100
L8C0.5NAd >5,000
V9C0.5>5,000500
V10C0.5>5,000NA
T11C0.55>5,000
A12C0.5500>5,000
  • a The lowest concentrations of CN-Cbl that allows formation of colonies of sizes comparable to those on methionine-supplemented medium are reported as in Table 1.

  • b The indicated btuB alleles were present in single gene copy at the attλ locus. Allele designations are as in Table 1. WT, wild type.

  • c Each btuB allele encoded the cysteine substitution indicated in the left column along with either no other amino acid substitution (Alone) or the L8P or V10P substitution.

  • d NA, not applicable.