Bacterial abl-like genes: production of the archaeal osmolyte Netext - acetyl - btext - lysine {N^{varepsilon }}{text{ - acetyl - }}beta {text{ - lysine}} by homologous overexpression of the yodP–kamA genes in Bacillus subtilis

摘要

Netext - acetyl - btext - lysine {N^{varepsilon }}{text{ - acetyl - }}beta {text{ - lysine}} is an archaeal compatible solute whose synthesis is mediated by the sequential reactions of the lysine-2,3-aminomutase AblA and the acetyltransferase AblB. α-Lysine serves as the precursor and is converted by AblA to β-lysine, and AblB then acetylates this intermediate to Netext - acetyl - btext - lysine {N^{varepsilon }}{text{ - acetyl - }}beta {text{ - lysine}} . The biochemical and biophysical properties of Netext - acetyl - btext - lysine {N^{varepsilon }}{text{ - acetyl - }}beta {text{ - lysine}} have so far not been studied intensively due to restrictions in the supply of this compound. A search for ablAB-like genes in the genomes of members of the family Bacillaceae revealed the yodP–kamA genes that encode a AblA-related lysine-2,3-aminomutase and AblB-related putative acetyltransferase. In Bacillus subtilis, the yodP–kamA genes are part of a transcriptional unit (yodT–yodS–yodR–yodQ–yodP–kamA) whose expression is upregulated during sporulation and controlled by the mother-cell-specific transcription factor SigE. Netext - acetyl - btext - lysine {N^{varepsilon }}{text{ - acetyl - }}beta {text{ - lysine}} was not detectable in vegetatively growing or osmotically stressed B. subtilis cells, and the deletion of the yodT–yodS–yodR–yodQ–yodP–kamA region had no noticeable effects on growth in rich or minimal media or osmotic stress resistance. However, when we expressed the yodP–kamA genes outside their natural genetic context from an isopropyl β-d-1-thiogalactopyranoside-inducible promoter on a plasmid in B. subtilis, the recombinant strain synthesized considerable amounts (0.28 μmol/mg protein) of Netext - acetyl - btext - lysine {N^{varepsilon }}{text{ - acetyl - }}beta {text{ - lysine}} . The data reported here thus open the bottleneck for the large-scale production of Netext - acetyl - btext - lysine {N^{varepsilon }}{text{ - acetyl - }}beta {text{ - lysine}} to investigate its properties as a compatible solute.