Protein-protein interaction of the Ro-ribonucleoprotein particle using multiple antigenic peptides

Protein-protein interactions play a significant role in maintaining the str uctural and functional integrity of the cell. We used multiple antigen pept ides (MAPs) to analyze such interactions within the Ro (or SSA) ribonucleop rotein complex. Our data showed that 60 kD Ro and La colocalize in the nucl eus of the cell. Previous data have indicated that 60 kD Po and La co-exist via interactions with the hYRNAs, We were interested to see whether 60 kD Ro and La interact with each other through protein-protein interactions. MA Ps were produced with sequences derived from the autoepitopes of 60 kD Ro, When used in agarose immunodiffusion certain MAPs formed precipitin lines s pecifically with Ro and La antigens. Used in affinity chromatography the Ro MAPs purified the Ro ribonucleoprotein particle from lymphocyte extract. S olid phase Immunoassay and surface plasmon resonance (SPR) confirmed the ob servations obtained with agarose diffusion. Using SPR, kinetic analyses gav e an apparent affinity constant of about 1 x 10(7) M-1 for Ro-MAP-60 kD Ro interactions. The autoantigens Ro and La are specific targets in autoimmune diseases, particularly systemic lupus erythematosus (SLE) and Sjogren's sy ndrome, and are known to exist together as a complex with hYRNAs. The prese nt data indicate that there are protein-protein interactions between Ro and La. Published by Elsevier Science Ltd.