Biophysical analysis of the interaction between B30.2 domain of GNIP/TRIM7 and glycogenin

MUÑOZ SOSA, CHRISTIAN J.; CARRIZO, MARÍA E.

San Luis

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Biofísica; 2019

Sociedad Argentina de Biofísica

The initiation of glycogen biosynthesis involves the self-glucosylation of glycogenin, that synthetizes a maltosaccharide upon which glycogen synthase and branching enzyme continue glucose polymerization. In a yeast two-hybrid screen for proteins that interact with glycogenin, a protein designated GNIP (Glycogenin Interacting Protein) was isolated. GNIP gene generates at least four isoforms, the largest of which (GNIP1) is predicted to have an N-terminal RING domain, a B-box domain, a coiled-coil region (RBCC motif); and a C-terminal B30.2 domain. The GNIP2 isoform, containing the B30.2 domain and a segment of the coiled-coil region, was found to stimulate glycogenin self-glucosylation in vitro while the B30.2 domain (GNIPB30.2) was reported to be necessary for the interaction with the enzyme.In the last few years, GNIP has also been named TRIM7 (Tripartite motif containing protein 7) and, as many members of the Trim protein family, has shown to have ubiquitin ligase activity and to be capable of autoubiquitination, with GNIP/TRIM7B30.2 having an essential role in this function.Very recently, we have solved the three-dimensional structure of human GNIP/TRIM7B30.2 in two different crystal forms (at 1.6 Å and 1.8 Å resolution). Now, in order to establish the region responsible for the interaction with glycogenin, we have prepared GNIP/TRIM7B30.2 mutants in residues selected from the analysis of its structure and the sequence conservation between several B30.2 domains. Here we show preliminary results, which suggest two of these amino acids would be involved in the interaction between GNIP/TRIM7B30.2 and human glycogenin.a - CIQUIBIC (CONICET - UNC), Centro de Investigaciones en Química Biológica de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, 5000, Córdoba, Argentina