Quantitation of de Novo Localized 15N-Labeled Lipoproteins and Membrane Proteins Having One and Two Transmembrane Segments in a Bacillus subtilis secA Temperature-Sensitive Mutant Using 2D-PAGE and MALDI-TOF MS

Abstract
We developed a means of quantifying proteins that have just localized in the cytoplasmic membrane using 15N-whole cell labeling together with 2D-PAGE and MALDI-TOF MS. The localization of 18 among 20 proteins consisting of 8 lipoproteins, 11 integral membrane proteins having one or two transmembrane segments and one secretory protein in the membrane fractions of Bacillus subtilis, was inhibited by the absence of SecA in a temperature-sensitive mutant. The time course of inhibition indicated that SecA participates in the localization of those proteins through immediately dependent, delayed dependent, and independent ways. Keywords: proteomics • membrane protein localization • SecA • stable isotope 15N • Bacillus subtilis • MALDI-TOF MS • 2D-PAGE