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Structure-function analysis of GNIP, the glycogenin-interacting protein
Lanmin Zhai1, Amy Dietrich, Alexander V Skurat
1Department of Biochemistry and Molecular Biology, Center for Diabetes Research, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202-5122, USA.
Archives of Biochemistry and Biophysics
|February 27, 2004
Summary
Glycogenin-interacting proteins (GNIPs), encoded by the TRIM7 gene, stimulate glycogen biosynthesis. The B30.2 domain of GNIPs mediates interaction with glycogenin, potentially forming multimeric complexes.
Area of Science:
- Biochemistry
- Molecular Biology
- Glycogen Metabolism
Background:
- Glycogenin initiates glycogen biosynthesis through self-glucosylation.
- Glycogenin-interacting proteins (GNIPs) were identified as stimulators of glycogenin activity.
- The GNIP gene (TRIM7) encodes multiple isoforms with shared domains.
Purpose of the Study:
- To characterize the interaction between GNIPs and glycogenin.
- To identify the specific domains responsible for GNIP-glycogenin interaction.
- To investigate self-interaction and hetero-interaction among GNIP isoforms.
Main Methods:
- Yeast two-hybrid system with deletion mutants of GNIP2.
- Western blot analysis for protein distribution.
- Glutaraldehyde cross-linking of recombinant GNIP2 and glycogenin.
Main Results:
- The B30.2 domain of GNIP2 mediates binding to glycogenin.
- A truncated GNIP2 lacking the N-terminal coiled-coil region still binds glycogenin.
- GNIP2 self-interaction occurs via the coiled-coil domain; GNIP1 and GNIP2 also interact.
- GNIP1 protein shows wide tissue distribution.
Conclusions:
- The B30.2 domain is crucial for GNIP-glycogenin interaction.
- GNIP isoforms can form homo- and hetero-oligomeric complexes.
- Complexes of glycogenin and GNIPs may form higher-order structures, influencing glycogen biosynthesis.