Title: Identification of a GTPase Activating Protein Specific for the Heterotrimeric G Protein, Gz
Abstract: Gz is a member of the Gi family of trimeric G proteins whose precise signalling function has not been defined. It can be distinguished from other members of the family by several interesting biochemical properties of its α subunit, Gzα. One particularly intriguing property is its extremely slow GTPase activity; its kcat for GTP hydrolysis is as much as 200-fold less than other Gα's. Since there is evidence that cellular factors can accelerate the GTPase activities of Gα subunits, we have suspected that cells expressing Gzα may contain a GTPase-activating protein, or GAP, that would enhance its hydrolytic ability. Using purified Gzα-GTP as a substrate, we have identified and characterized such a GAP that acts on Gzα, which we have termed Gz-GAP. The protein responsible for this activity is specific for Gzα and is found in the membrane fraction of bovine brain and in several other tissues that express Gz. Since G protein effectors are in many cases capable of stimulating the GTPases rate of Gα subunits, we speculate that a novel effector for Gz is responsible for the activity.
Publication Year: 1998
Publication Date: 1998-01-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 6
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