Sulfur-limitation-regulated proteins in Bacillus subtilis: a two-dimensional gel electrophoresis study

Little is known about the genes and enzymes involved in sulfur assimilation in Bacillus subtilis, or about the regulation of their expression or activ ity. To identify genes regulated by sulfur limitation, the authors used two -dimensional (2D) gel electrophoresis to compare the proteome of a wild-typ e strain grown with either sulfate or glutathione as sole sulfur source. A total of 15 proteins whose synthesis is modified under these two conditions were identified by matrix-assisted laser desorption/ionization time of fli ght (MALDI TOF) mass spectrometry, In the presence of sulfate, an increased amount of proteins involved in the metabolism of C, units (SerA, GlyA, Fol D) and in the biosynthesis of purines (PurQ, Xpt) and pyrimidines (Upp, Pyr AA, PyrF) was observed. In the presence of glutathione, the synthesis of tw o uptake systems (DppE, SsuA), an oxygenase (SsuD), cysteine synthase (CysK ) and two proteins of unknown function (Ytml, YurL) was increased. The chan ges in expression of the corresponding genes, in the presence of sulfate an d glutathione, were monitored using slot-blot analyses and lacZ fusions, Th e ytml gene is part of a locus of 12 genes which are co-regulated in respon se to sulfur availability. This putative operon is activated by a LysR-like regulator, Ytll, This is the first regulator involved in the control of ex pression in response to sulfur availability to be identified in a, subtilis .