Surface proteins of typhus and spotted fever group rickettsiae

Abstract

Six proteins, previously established as major constituents of intact organisms were identified in cell envelopes obtained from intrinsically radiolabeled Rickettsia prowazekii. Extrinsic radioiodination of intact organisms conducted at 0.5 !LM iodide indicated that protein 4 was the most peripheral, although protein 1 also had reactive groups exposed on the surface of the organisms. A 10-fold increase in iodide concentration resulted in labeling of protein 2, and at 50 ,uM iodide, all six major proteins were radiolabeled. Similar selective labeling was not achieved with R. conorii. Analysis of both typhus and spotted fever group organisms radiolabeled with galactose suggested that carbohydrate was associated with proteins 1, 3, and 4. Typhus soluble antigen included all major proteins except protein 2, which remained attached to particulate rickettsiae after ether extraction. Protein 4 appeared to be prominent in the surface topography of R. prowazekii, was a component of soluble antigen and may have an important role in rickettsiae-host interactions.

Mitochondrial Porin VDAC 1 Seems to Be Functional in Rickettsial Cells

“…First method is known to produce OM fraction, whereas the second one produces TM (see above). Polypeptide composition of OM fraction proved to be essentially the same as described by other researchers using different methods, such as extrinsic iodination 26,27 and fractionation of total R. prowazekii membranes on sucrose density gradients. 28 The above crude OM fraction was shown to contain integral OM proteins (OMPs), but not mitochondrial porin, while fraction of TM contained a variety of minor proteins, OMPs and VDAC 1.…”

Identification and characterization of Vibrio cholerae surface proteins by radioiodination

“…These studies and others (16,17,34) indicate that the outer membrane of V. cholerae is a complex structure containing many proteins.Proteins exposed on the bacterial surface are likely to contribute to colonization of the host, and improved knowledge of the surface proteins should further our understanding of their role in colonization. The surface proteins of several bacterial species have been identified by iodination with membrane-impermeable enzymes (15,20,29,31) or the water-insoluble reagent, 1,3,4,6-tetrachloro-3,6-diphenylglycouril (Iodogen) (33). We used lodogen-coated vessels and a covalently immobilized catalyst (lodo-beads) to radioiodinate whole cells and isolated outer membrane of V. cholerae.…”

Cloning, expression and sequence analysis of the gene encoding the 120kD surface‐exposed protein of Rickettsia rickettsii

“…Few prokaryotic polypeptides are glycosylated, an exception being some crystalline surface-layer proteins, or S layers, found in several prokaryotic species (Sletyr and Messner, 1988). There is also some evidence to indicate that surface proteins of the typhus and spotted fever group rickettsiae may be glycosylated (Osterman and Eisemann, 1978). Since there are no known glycosylation mechanisms in prokaryotes.…”