Structural characterization of ordered arrays of sn-glycerol-3-phosphate acyltransferase from Escherichia coli

摘要: Overproduction of the sn-glycerol-3-phosphate acyltransferase in Escherichia coli leads to incorporation this integral membrane protein into ordered tubular arrays within cell. Freeze-fracture-etch shadowing was performed on suspensions partially purified tubules and whole bacteria. This procedure revealed presence ridges grooves defining a set long-pitch left-handed helical ridges. The helices represented chains dimers. Tubules observed cell were often closely packed, with an apparent alignment adjacent tubules. Fracture planes passing through indicated bilayer structure, some portion enzyme being associated membrane. major extended from hydrophilic surface, forming large globular structure that, favorable views, displayed central cavity facing cytoplasm. Computer analysis shadowed that six stranded, pitch 1,050 A (105.0 nm) spacing 75 (7.5 between dimers along chains. Analysis predicted secondary failed reveal obvious transmembrane segments, suggesting very little inserted bilayer.