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

The initiation of glycogen biosynthesis involves the self-glucosylation of glycogenin, thatsynthetizes a maltosaccharide upon which glycogen synthase and branching enzymecontinue glucose polymerization. In a yeast two-hybrid screen for proteins that interactwith glycogenin, a protein designated GNIP (Glycogenin Interacting Protein) was isolated.GNIP gene generates at least four isoforms, the largest of which (GNIP1) is predicted tohave an N-terminal RING domain, a B-box domain, a coiled-coil region (RBCC motif); anda C-terminal B30.2 domain. The GNIP2 isoform, containing the B30.2 domain and asegment of the coiled-coil region, was found to stimulate glycogenin self-glucosylation invitro while the B30.2 domain (GNIPB30.2) was reported to be necessary for the interactionwith the enzyme.In the last few years, GNIP has also been named TRIM7 (Tripartite motif containingprotein 7) and, as many members of the Trim protein family, has shown to have ubiquitinligase activity and to be capable of autoubiquitination, with GNIP/TRIM7B30.2 having anessential role in this function.Very recently, we have solved the three-dimensional structure of human GNIP/TRIM7B30.2in two different crystal forms (at 1.6 Å and 1.8 Å resolution). Now, in order to establishthe region responsible for the interaction with glycogenin, we have prepared GNIP/TRIM7B30.2 mutants in residues selected from the analysis of its structure and thesequence conservation between several B30.2 domains. Here we show preliminaryresults, which suggest two of these amino acids would be involved in the interactionbetween GNIP/TRIM7B30.2 and human glycogenin.