The alpha-chain of murine CD8 lacks an invariant Ig-like disulfide bond but contains a unique intrachain loop instead.
The CD8 Ag is a cell surface heterodimer which demarcates predominantly cytotoxic T cells which are restricted by class I MHC Ag. The disulfide bonds within the murine structure were assigned in this study and the alpha-beta-interchain bond involves one or more cysteine residues located in each chain proximal to the plasma membrane or included within it. The location of the intrachain disulfide loop within the CD8 beta-chain confirms its proposed structural homology to an IgV domain but no corresponding disulfide loop is present within the alpha-chain. The invariant IgV disulfide loop has been replaced by a unique, short loop involving an unusual cysteine which is conserved in the CD8 alpha-chains of man, mouse, and rat. Despite its lack of precedent in other Ig-related structures, this unusual disulfide loop can be parsimoniously accommodated into a modified domain which has retained the major features of the Ig structural motif.
Kirszbaum
L
L
Department of Veterinary Preclinical Sciences, University of Melbourne, Victoria, Australia.
Sharpe
J A
JA
Goss
N
N
Lahnstein
J
J
Walker
I D
ID
D000595:Amino Acid Sequence; D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000302:isolation & purification*; D016827:CD8 Antigens; D004220:Disulfides; D005260:Female; D007135:Immunoglobulin Variable Region / Q000302:isolation & purification*; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification; D011487:Protein Conformation; D013329:Structure-Activity Relationship
D000945:Antigens, Differentiation, T-Lymphocyte; D016827:CD8 Antigens; D004220:Disulfides; D007135:Immunoglobulin Variable Region; D010446:Peptide Fragments