Activation of G Protein-Coupled Receptor Kinase 1 Involves Interactions between Its N-Terminal Region and Its Kinase Domain

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• 作者：Chih-chin Huang ; Tivadar Orban ; Beata Jastrzebska ; Krzysztof Palczewski ; John J. G. Tesmer
• 刊名：Biochemistry
• 出版年：2011
• 出版时间：March 22, 2011
• 年：2011
• 卷：50
• 期：11
• 页码：1940-1949
• 全文大小：1065K
• 年卷期：v.50,no.11(March 22, 2011)
• ISSN：1520-4995

文摘

G protein-coupled receptor kinases (GRKs) phosphorylate activated G protein-coupled receptors (GPCRs) to initiate receptor desensitization. In addition to the canonical phosphoacceptor site of the kinase domain, activated receptors bind to a distinct docking site that confers higher affinity and activates GRKs allosterically. Recent mutagenesis and structural studies support a model in which receptor docking activates a GRK by stabilizing the interaction of its 20-amino acid N-terminal region with the kinase domain. This interaction in turn stabilizes a closed, more active conformation of the enzyme. To investigate the importance of this interaction for the process of GRK activation, we first validated the functionality of the N-terminal region in rhodopsin kinase (GRK1) by site-directed mutagenesis and then introduced a disulfide bond to cross-link the N-terminal region of GRK1 with its specific binding site on the kinase domain. Characterization of the kinetic and biophysical properties of the cross-linked protein showed that disulfide bond formation greatly enhances the catalytic efficiency of the peptide phosphorylation, but receptor-dependent phosphorylation, Meta II stabilization, and inhibition of transducin activation were unaffected. These data indicate that the interaction of the N-terminal region with the kinase domain is important for GRK activation but does not dictate the affinity of GRKs for activated receptors.