Structural studies of the putative helix 8 in the human beta(2) adrenergic receptor: an NMR study |
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Authors: | Katragadda M Maciejewski M W Yeagle P L |
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Institution: | Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, U-3125, Storrs, CT 06269-3125, USA. |
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Abstract: | The recently reported crystal structure of bovine rhodopsin revealed a cytoplasmic helix (helix 8) in addition to the seven transmembrane helices. This domain is roughly perpendicular to the transmembrane bundle in the presence of an interface and may be a loop-like structure in the absence of an interface. Several studies carried out on this domain suggested that it might act as a conformational switch between the inactive and activated states of this G-protein coupled receptor (GPCR). These results raised the question whether helix 8 may be an important feature of other GPCRs as well. To explore this question, we determined the structure of a peptide representing the putative helix 8 domain in another receptor that belongs to the rhodopsin family of GPCRs, the human beta(2) adrenergic receptor (hbeta(2)AR), using two-dimensional (1)H nuclear magnetic resonance (NMR). The key results from this structural study are that the putative helix 8 domain is helical in detergent and in DMSO while in water this region is disordered; the conformation is therefore dependent upon the environment. Comparison of data from five GPCRs suggests that these observations may be generally important for GPCR structure and function. |
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