Electric properties of photoaffinity-labelled pancreatic A-subtype cholecystokinin.
Although the isoelectric point of a protein is very important, electric focusing of intrinsic membrane proteins in polyacrylamide or agarose gels often fails. The recently introduced Bio-Rad Rotofor cell allowed isoelectric focusing of such a protein, cholecystokinin (CCK) receptor. Both the isoelectric point and the molecular weight (Mr) of pancreatic CCK receptor were determined. For this purpose, membrane CCK receptor was photoaffinity labelled by a cleavable agonist probe, subsequently prepurified on immobilized wheat germ agglutinin and analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis and isoelectrofocusing in solution in the presence of Nonidet P-40. CCK receptor was identified at Mr 85,000-100,000, whereas its deglycosylated product was shifted to Mr 42,000. Further, the isoelectric points of the glycosylated and deglycosylated forms of CCK receptor were pH 4.8 and 4.3, respectively. A knowledge of the isoelectric point should help in characterizing better CCK receptor heterogeneity and/or in purifying CCK receptor proteins.
INSERM U 151, CHU Rangueil, Toulouse, France.
J
J
Jiménez
M
M
Dufresne
S
S
Poirot
N
N
Vaysse
D
D
Fourmy
D000345:Affinity Labels; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry; D002766:Cholecystokinin / Q000032:analysis*; D004563:Electrochemistry; D066298:In Vitro Techniques; D007525:Isoelectric Focusing; D037102:Lectins; D008297:Male; D008970:Molecular Weight; D010179:Pancreas / Q000201:enzymology*; D010777:Photochemistry; D051381:Rats; D011919:Rats, Inbred Strains; D011949:Receptors, Cholecystokinin / Q000032:analysis / Q000378:metabolism
D000345:Affinity Labels; D037102:Lectins; D011949:Receptors, Cholecystokinin; D002766:Cholecystokinin