In this report we demonstrate that the ion pair Arg-80 and Asp-57, located in the peptide-binding site of nearly all class II major histocompatibility complex (MHC) proteins, is important for surface expression and function of the murine class II heterodimer I-A. Charge reversal at either of these two residues by site-directed mutagenesis generated mutant class II molecules that failed to appear at the cell surface. This defect in surface expression was partially reversed when the invariant chain was present or when the mutants were paired with the corresponding charge-reversed variant of the opposite chain. Surprisingly, surface expression was restored when cells expressing the single-site mutants were cultured at reduced temperature. In addition, the substitution of Asp-57 with residues found in alleles of class II molecules associated with diabetes resulted in heterodimers that were inefficiently expressed at the cell surface and presented foreign peptide poorly. Together, these results demonstrate that the formation of a salt-bridge between Arg-80 and Asp-57 is required for efficient surface expression of class II MHC molecules, therefore representing an important step in the assembly and transport of functional class II heterodimers to the cell surface.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				B. A. Rybicki, M. J. Maliarik, L. M. Poisson, R. Sheffer, K. M. Chen, M. Major, G. A. Chase, and M. C. Iannuzzi The Major Histocompatibility Complex Gene Region and Sarcoidosis Susceptibility in African Americans Am. J. Respir. Crit. Care Med., February 1, 2003; 167(3): 444 - 449. [Abstract] [Full Text] [PDF]

				V. Kumar, M. Rajadhyaksha, and J. Wortsman Celiac Disease-Associated Autoimmune Endocrinopathies Clin. Vaccine Immunol., July 1, 2001; 8(4): 678 - 685. [Abstract] [Full Text] [PDF]

				L. S. Arneson, M. Peterson, and A. J. Sant The MHC Class II Molecule I-Ag7 Exists in Alternate Conformations That Are Peptide Dependent J. Immunol., August 15, 2000; 165(4): 2059 - 2067. [Abstract] [Full Text] [PDF]

				A. L. Corper, T. Stratmann, V. Apostolopoulos, C. A. Scott, K. C. Garcia, A. S. Kang, I. A. Wilson, and L. Teyton A Structural Framework for Deciphering the Link Between I-Ag7 and Autoimmune Diabetes Science, April 21, 2000; 288(5465): 505 - 511. [Abstract] [Full Text]

				M. Peterson and A. J. Sant The Inability of the Nonobese Diabetic Class II Molecule to Form Stable Peptide Complexes Does Not Reflect a Failure to Interact Productively with DM J. Immunol., September 15, 1998; 161(6): 2961 - 2967. [Abstract] [Full Text] [PDF]

				F. J. Garcia-Cozar, H. Okamura, J. F. Aramburu, K. T. Y. Shaw, L. Pelletier, R. Showalter, E. Villafranca, and A. Rao Two-site Interaction of Nuclear Factor of Activated T Cells with Activated Calcineurin J. Biol. Chem., September 11, 1998; 273(37): 23877 - 23883. [Abstract] [Full Text] [PDF]