Dual channel imaging of two‐dimensional electropherograms in Bacillus subtilis

The allocation of proteins to stimulons and regulons is an essential step towards the understanding of the global regulation of the expression of entire genomes. The computer‐aided evaluation and matching of two‐dimensional protein gels loaded with radioactively labeled proteins from exponentially growing or stressed cells is a useful but time‐consuming procedure for the description of stimulons and regulons. This paper describes the dual‐channel image analysis that offers the opportunity to visualize the content and synthesis rate of a whole set of bacterial proteins on a single electropherogram. By pulse‐labeling with L‐[35S]methionine, the protein synthesis pattern (red color) can be directly compared with the protein level pattern (green color). Because matching of other gels can be avoided, this new technique is useful for the rapid search for proteins that belong to different stimulons or regulons. This approach was tested for the identification of proteins of heat stress or oxidative stress stimulons. Proteins that were induced by heat or oxidative stress colored red while proteins whose synthesis was switched off by the stress factor colored green. Proteins that were continuously synthesized before and after the imposition of stress retained their yellow color. The advantages and possible pitfalls of the technique are discussed.