phosphor (IMAGE) University of California - San Diego Caption Growth factors trigger G proteins (in green) to disengage from GPCRs and change localization within cells. At right: A ribbon diagram of the G protein structure shows the position of all phosphoevents the “buzzer” site in red. Credit UC San Diego Health Sciences Usage Restrictions use photo credit License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.