The disulfide structure of mouse lysosome-associated membrane protein 1.
The disulfide structure of mouse lysosome-associated membrane protein 1 has been determined by reverse-phase isolation and sequence analysis of the cysteine-containing tryptic fragments of the reduced and non-reduced deglycosylated protein. Half-cystines were distinguished (a) by their localization within tryptic or chymotryptic peptides that formed reverse-phase peaks unique to the reduced digests and (b) by their 3H-carboxymethylation only after reduction of the protein. The disulfide arrangement of the cysteines was assigned after isolation of disulfide-linked peptide pairs. Each pair chromatographed as a peak present in the nonreduced (but not the corresponding reduced) tryptic digest. NH2-terminal sequencing as well as reduction, alkylation, and rechromatography of the disulfide-linked fragments led to the following assignment of disulfide bonds: Cys11 and Cys50, Cys125 and Cys161, Cys198 and Cys235, and Cys303 and Cys340. This structure creates four 36-38-residue loops that are symmetrically placed within the two halves of the protein's intraluminal domain. The loops formed by the Cys11-Cys50 and Cys198-Cys235 bridges are homologous, and the Cys125-Cys161 and Cys303-cys340 loops form a second set of homologous domains. The conservation of cysteine residues among lysosome-associated membrane proteins 1 and 2 suggests that this disulfide arrangement is common to both members of this family of lysosomal membrane glycoproteins.
Arterburn
L M
LM
Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Earles
B J
BJ
August
J T
JT
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D002918:Chymotrypsin; D003553:Cystine / Q000032:analysis; D004220:Disulfides / Q000032:analysis; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins / Q000302:isolation & purification; D051379:Mice; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid; D014357:Trypsin
D015703:Antigens, CD; D004220:Disulfides; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D003553:Cystine; D002918:Chymotrypsin; D014357:Trypsin