Molecular NeuroscienceAlanine-23 of transducin α subunit is involved in defining the affinity for βγ complexChung Ho, Maurice Kwok1; Wong, Yung Hou1,2Author Information Department of Biology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China. 2Corresponding Author: Yung Hou Wong ACKNOWLEDGEMENTS: We thank Randall Reed for AC2 cDNA and Christopher Evans for the mouse DOR cDNA. This work was supported in part by grants (HKUST 567/95M and 6096/98M) from the Research Grants Council of Hong Kong. Received 26 January 1999; accepted 17 March 1999 NeuroReport: June 23rd, 1999 - Volume 10 - Issue 9 - p 1993-1996 Buy Abstract TRANSDUCIN α subunit (αt1) shows extraordinarily high affinity to G protein βγ complex. One of the βγ-binding regions on αt1 is the amino-terminal helix. Alanine-23 is uniquely found on αt1 but not other members of the Gi-subfamily. Mutation of alanine-23 into serine reduced the ability of αt1 to sequester βγ-mediated stimulation of type II adenylyl cyclase. The functional impairment is independent to the protein expression levels. Molecular modeling indicated that the hydrophobic interaction between the side chains of alanine-23 of αt1 and leucine-55 of the β1 subunit could be disrupted by the introduction of a hydroxyl group. This study showed that alanine-23 of αt1 is probably involved in defining its affinity for the βγ complex © 1999 Lippincott Williams & Wilkins, Inc.