Molecule Found that Modulates G Protein Degradation

Researchers have found that GAIP interacting protein N terminus (GIPN), a component of the ubiquitin system, plays a key role in the degradation of G proteins, a family of proteins located in the intracellular portion of the plasma membrane. These proteins bind activated receptor complexes and, through conformational changes and cyclic binding and hydrolysis of GTP, directly or indirectly effect alterations in channel gating, thereby coupling cell surface receptors to intracellular responses.

Investigators the University of California, San Diego (USA) isolated GIPN and showed that it was a 38-kDa protein with an N-terminal leucine-rich region, a central RING finger-like domain, and a putative C-terminal transmembrane domain. GIPN bound exclusively to RGS proteins of subfamily A, RGS-GAIP, RGSZ1, and RGSZ2. These findings were published in the July 8, 2003, issue of the Proceedings of the National Academy of Sciences.

"As usual with scientific projects like this one, you have to go much more into the details of the mechanism,” said senior author Dr. Marilyn Farquhar, chairperson of the department of cellular and molecular medicine at the University of California, San Diego. "We have a number of experiments now underway to firm up the precise mechanism. Discovery is finding something new, in this case, a new protein. Then, it takes a long time to work out the biology.”