Chemical Characterization, Spatial Distribution and Function of a Lipoprotein (Murein-Lipoprotein) of the E. coli Cell Wall. The Specific Effect of Trypsin on the Membrane Structure

作者：V Braun, Kurt Georg Rehn · 发表于：European Journal of Biochemistry · 年份：1969 · DOI：10.1111/j.1432-1033.1969.tb00707.x · 被引用次数：553 · 研究领域：Protein Structure and Dynamics、Enzyme Structure and Function、Glycosylation and Glycoproteins Research

A decrease of the absorbance at 578 nm of a cell wall suspension of mid log phase E. coli occurs when the suspension is incubated with trypsin. The reaction is so rapid that 55% of the total decrease is obtained within the first 2 min [ratio of enzyme to total cell wall protein = 1: 50 (w/w), room temperature]. The rate of the reaction is specific for trypsin when compared with other proteases, different lipases, lysozyme and other glycosidases. A peptide bond especially sensitive to trypsin could be localized within the complex cell wall by the demonstration that the decrease of the absorbance is paralleled by the splitting of the protein from the murein. This protein could be shown to be a lipoprotein with a part of the lipid probably covalently bound to the protein. It is called murein-lipoprotein. The link between the lipoprotein and the murein is -lysine. After trypsin digestion lysine is the only additional amino acid remaining at the murein. The ratio of the amount of lysine to the known constituents of the murein demonsstrates that on the average one lipoprotein molecule is covalently bound to every tenth repeating unit of the murein (N-acetylglucosamine–N-acetylmuramic acid–l-alanine-d-glutamic acid–meso-diaminopimelic acid–d-alanine). After 3 min incubation with trypsin, the isolated lipoprotein molecules have a lysine to arginine ratio of 4:4 as compared with 5:4 in the native molecule. The lipoprotein has an unusual amino acid comosition since it contains about 65...