|
|
|
|
|
|
|
||
J. Exp. Med.,
Volume 188, Number 11, December 7, 1998 2139-2149
By
From the * Department of Pathology, and To characterize the importance of a highly conserved region of the class II Committees on Immunology and Cancer Biology,
University of Chicago, Illinois 60637; and the § Department of Biochemistry, Molecular Biology, and
Cell Biology, Northwestern University, Evanston, Illinois 60208
chain, we introduced an amino acid substitution that is predicted to eliminate a hydrogen bond formed between the class II molecule and peptide. We expressed the mutated chain with a wild-type 
chain in a murine L cell by gene transfection. The mutant class II molecule (81H
) assembles
normally in the endoplasmic reticulum and transits the Golgi complex. When invariant chain (Ii)
is coexpressed with 81H, the class II-Ii complex is degraded in the endosomes. Expression of
81H in the absence of Ii results in a cell surface expressed molecule that is susceptible to proteolysis, a condition reversed by incubation with a peptide known to associate with 81H.
We propose that 81H is protease sensitive because it is unable to productively associate with
most peptides, including classII-associated invariant chain peptides. This model is supported by
our data demonstrating protease sensitivity of peptide-free wild-type I-Ad molecules. Collectively, our results suggest both that the hydrogen bonds formed between the class II molecule
and peptide are important for the integrity and stability of the complex, and that empty class II
molecules are protease sensitive and degraded in endosomes. One function of DM may be to
insure continuous groove occupancy of the class II molecule.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
| TABLE OF CONTENTS |
|
