Identification of thiol groups and a disulfide crosslink site in bovine myelin proteolipid protein.
The existence of disulfide crosslinks limits the number of possible folded structures a protein can assume. Thus localization of disulfide and thiol groups is a key to understanding the conformation and orientation of myelin proteolipid protein (PLP) in the myelin membrane. [14C]Carboxamidomethylated PLP was fragmented with chymotrypsin, and the resulting mixture was partially separated by reversed-phase HPLC. Purified 14C-labeled peptides and a disulfide containing peptide were characterized by amino acid analysis. These experiments showed that Cys-32 and Cys-34 are free thiols, and are presumably on the interior of the cell or within the membrane bilayer, and that Cys-200 and Cys-219 are joined by a disulfide bond, and are probably located on the extracellular face of the membrane. Sequence analysis experiments indicate that Cys-5, Cys-6 and Cys-9 are linked by disulfides, probably to other parts of the protein on the extracellular face of the membrane.
Shaw
S Y
SY
Department of Chemistry, Boston University, MA 02215.
Laursen
R A
RA
Lees
M B
MB
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D003432:Cross-Linking Reagents; D004220:Disulfides / Q000032:analysis*; D008051:Lipid Bilayers / Q000032:analysis; D009185:Myelin Proteins / Q000032:analysis*; D018991:Myelin Proteolipid Protein; D013438:Sulfhydryl Compounds / Q000032:analysis*
D000596:Amino Acids; D003432:Cross-Linking Reagents; D004220:Disulfides; D008051:Lipid Bilayers; D009185:Myelin Proteins; D018991:Myelin Proteolipid Protein; D013438:Sulfhydryl Compounds