Sequencing revealed a T to A transversion that resulted in a leucine to glutamine substitution in a segment predicted to form a coiled coil (CC) domain, and is conserved in the heptad repeats of the predicted alpha-helical coil. Western blot revealed normal levels of protein in mutant B cells. The change from nonpolar leucine to polar glutamine putatively disrupts the CC structure and interferes with protein pairing. (J:84042)