Differences in the dimerization properties mediated by the transmembrane domains of Zea mays and Arabidopsis CRINKLY4 AND CRINKLY4‐like receptor kinases

Abstract

CRINKLY4 is a transmembrane (TM) containing serine/threonine receptor kinase that functions in the differentiation of the leaf epidermis and the aleurone cell layer in Z. mays (ZmCR4) and development of the integument and seed coat in Arabidopsis (AtCR4). In addition, the Arabidopsis genome also encodes four CRINKLY4 homologs whose functions are not known. Based on studies of animal receptor kinase proteins, it is likely that CRINKLY4, and its homologs, also function as dimers. The importance of the TM domain in the dimerization of several receptor kinases has been demonstrated by the TOXCAT system, a genetic assay that measures helix interactions in a natural membrane environment. In this study, we have used the TOXCAT assay to investigate the potential of the CRINKLY4 and CRINKLY4‐like TM domains to homodimerize. Our investigation indicates that the ZmCR4 TM domain and the Arabidopsis homologs have similar homodimerization potentials. In contrast, the dimerization potential of the AtCR4 TM domain is significantly weaker, which suggests that the functional mechanisms of ZmCR4 and AtCR4 may be different. Interestingly, 13 of 24 amino acids are identical between the ZmCR4 and AtCR4 TM domains. We also report on studies aimed at delineating the contribution of specific amino acids to differences in the dimerization potential of CRINKLY4 TM domains of the two organisms.