Crystal Structure of the Ectodomain Complex of the CGRP Receptor, a Class-B GPCR, Reveals the Site of Drug Antagonism

Modelling class B G-protein-coupled receptors (GPCRs) using class A GPCR structural templates is difficult due to lack of homology. The plant GPCR, GCR1, has homology to both class A and class B GPCRs. We have used this to generate a class A–class B alignment, and by incorporating maximum lagged correlation of entropy and hydrophobicity into a consensus score, we have been able to align receptor transmembrane regions. We have applied this analysis to generate active and inactive homology models of the class B calcitonin gene-related peptide (CGRP) receptor, and have supported it with site-directed mutagenesis data using 122 CGRP receptor residues and 144 published mutagenesis results on other class B GPCRs. The variation of sequence variability with structure, the analysis of polarity violations, the alignment of group-conserved residues and the mutagenesis results at 27 key positions were particularly informative in distinguishing between the proposed and plausible alternative alignments. Furthermore, we have been able to associate the key molecular features of the class B GPCR signalling machinery with their class A counterparts for the first time. These include the [K/R]KLH motif in intracellular loop 1, [I/L]xxxL and KxxK at the intracellular end of TM5 and TM6, the NPXXY/VAVLY motif on TM7 and small group-conserved residues in TM1, TM2, TM3 and TM7. The equivalent of the class A DRY motif is proposed to involve Arg 2.39 , His 2.43 and Glu 3.46 , which makes a polar lock with T 6.37 . These alignments and models provide useful tools for understanding class B GPCR function.

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The VPAC1 receptor: structure and function of a class B GPCR prototype

Frontiers in Endocrinology ◽

10.3389/fendo.2012.00139 ◽

2012 ◽

Vol 3 ◽

Cited By ~ 10

Author(s):

A. Couvineau ◽

E. Ceraudo ◽

Y.-V. Tan ◽

P. Nicole ◽

M. Laburthe

Keyword(s):

Structure And Function ◽

Receptor Structure ◽

Vpac1 Receptor ◽

Class B ◽

And Function ◽

Class B Gpcr

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X-ray Structure of the ZnII β-Lactamase from Bacteroides fragilis in an Orthorhombic Crystal Form

Acta Crystallographica Section D Biological Crystallography ◽

10.1107/s090744499700927x ◽

1998 ◽

Vol 54 (1) ◽

pp. 47-57 ◽

Cited By ~ 45

Author(s):

Andrea Carfi ◽

Emile Duée ◽

Raquel Paul-Soto ◽

Moreno Galleni ◽

Jean-Marie Frère ◽

...

Keyword(s):

Crystal Structure ◽

Catalytic Mechanism ◽

Bacteroides Fragilis ◽

Crystal Form ◽

Water Molecules ◽

Orthorhombic Crystal ◽

X Ray ◽

Class B ◽

Catalytic Mechanisms ◽

Zn Ions

β-Lactamases are extracellular or periplasmic bacterial enzymes which confer resistance to β-lactam antibiotics. On the basis of their catalytic mechanisms, they can be divided into two major groups: active-site serine enzymes (classes A, C and D) and the ZnII enzymes (class B). The first crystal structure of a class B enzyme, the metallo-β-lactamase from Bacillus cereus, has been solved at 2.5 Å resolution [Carfi, Pares, Duée, Galleni, Duez, Frère & Dideberg (1995). EMBO J. 14, 4914–4921]. Recently, the crystal structure of the metallo-β-lactamase from Bacteroides fragilis has been determined in a tetragonal space group [Concha, Rasmussen, Bush & Herzberg (1996). Structure, 4, 823–836]. The structure of the metallo-β-lactamase from B. fragilis in an orthorhombic crystal form at 2.0 Å resolution is reported here. The final crystallographic R is 0.196 for all the 32 501 observed reflections in the range 10–2.0 Å. The refined model includes 458 residues, 437 water molecules, four zinc and two sodium ions. These structures are discussed with reference to Zn binding and activity. A catalytic mechanism is proposed which is coherent with metallo-β-lactamases being active with either one Zn ion (as in Aeromonas hydrophila) or two Zn ions (as in B. fragilis) bound to the protein.

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