Diazoniobenzenesulfonate as marker for cell surface proteins: study of the surface coat of Trypanosoma congolense.

It is possible to label selectively the surface coat of Trypanosoma congolense with radioactive sulfanilic acid diazonium salt. As demonstrated by both sodium dodecylsulfate polyacrylamide gel electrophoresis and isoelectric focusing, radioactivity is incorporated into only one protein, which has a molecular weight of 57 000 and an isoelectric point of 6.25. This indicates that the surface coat of T. congolense is a homogeneous layer, composed of molecules of one type of protein.