Identification of the PEG-induced proteins by 2D-gel electrophoresis and mass spectrometry in Sphingopyxis macrogoltabida strain 103

Cell-free extracts from a PEG 4000-utilizing bacterium, Sphingopyxis macrogoltabida strain 103, grown on glucose and PEG 4000 medium were separated into cytoplasmic, membrane-bound and signal protein fractions. Each fraction was analyzed by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). A total of 19 differentially-expressed proteins by PEG were in-gel trypsin digested and the digestion mixtures were analyzed by MALDI-TOF mass spectrometry to determine the molecular masses of the resulting tryptic peptides. Ten proteins in the cytoplasmic fraction showed homology to fatty acyl CoA synthetase, IEA two-component response regulator, permease, LacI-transcription regulator, galactinol synthase, coenzyme PQQ synthesis protein, transcription regulator, translation-initiation factor like protein, CheY-like two-component response regulator and hypothetical protein. Three proteins in the membrane-bound fraction were identified as LysR-transcription regulator, GutR-transcription regulator and two-component response regulator. Six proteins in the signal protein fraction were polyphosphate kinase, ATP sulfurylase, amino acid permease, sigma-54 dependent transcription regulator, fatty-acid-CoA ligase and LysR-transcription regulator. These proteins are expected to be relevant to PEG metabolism by S. macrogoltabida strain 103.