Dual channel imaging of two-dimensional electropherograms in Bacillus subtilis

The allocation of proteins to stimulons and regulons is an essential step t owards the understanding of the global regulation of the expression of enti re genomes. The computer-aided evaluation and matching of two-dimensional p rotein gels loaded with radioactively labeled proteins from exponentially g rowing or stressed cells is a useful but time-consuming procedure for the d escription of stimulons and regulons. This paper describes the dual-channel image analysis that offers the opportunity to visualize the content and sy nthesis rate of a whole set of bacterial proteins on a single electropherog ram. By pulse-labeling with L-[S-35]methionine, the protein synthesis patte rn (red color) can be directly compared with the protein level pattern (gre en color). Because matching of other gels can be avoided, this new techniqu e is useful for the rapid search for proteins that belong to different stim ulons or regulons. This approach was tested for the identification of prote ins of heat stress or oxidative stress stimulons. Proteins that were induce d by heat or oxidative stress colored red while proteins whose synthesis wa s switched off by the stress factor colored green. Proteins that were conti nuously synthesized before and after the imposition of stress retained thei r yellow color. The advantages and possible pitfalls of the technique are d iscussed.