title: Structure of the RGS-like domain from PDZ-RhoGEF: linking heterotrimeric g protein-coupled signaling to Rho GTPases.
abstract: BACKGROUND
  The multidomain PDZ-RhoGEF is one of many known guanine nucleotide exchange factors that upregulate Rho GTPases. PDZ-RhoGEF and related family members play a critical role in a molecular signaling pathway from heterotrimeric G protein-coupled receptors to Rho proteins. A approximately 200 residue RGS-like (RGSL) domain in PDZ-RhoGEF and its homologs is responsible for the direct association with Galpha12/13 proteins. To better understand structure-function relationships, we initiated crystallographic studies of the RGSL domain from human PDZ-RhoGEF.
  
  
  RESULTS
  A recombinant construct of the RGSL domain was expressed in Escherichia coli and purified, but it did not crystallize. Alternative constructs were designed based on a novel strategy of targeting lysine and glutamic acid residues for mutagenesis to alanine. A triple-point mutant functionally identical to the wild-type protein was crystallized, and its structure was determined by the MAD method using Se-methionine (Se-Met) incorporation. A molecular model of the RGSL domain was refined at 2.2 A resolution, revealing an all-helical tertiary fold with the mutations located at intermolecular lattice contacts.
  
  
  CONCLUSIONS
  The first nine helices adopt a fold similar to that observed for RGS proteins, although the sequence identity with other such known structures is below 20%. The last three helices are an integral extension of the RGS fold, packing tightly against helices 3 and 4 with multiple hydrophobic interactions. Comparison with RGS proteins suggests features that are likely relevant for interaction with G proteins. Finally, we conclude that the strategy used to produce crystals was beneficial and might be applicable to other proteins resistant to crystallization.
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, P.O. Box 800736, Charlottesville, VA 22908, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Longenecker
authors.forename: M E
authors.initials: ME
authors.lastname: Lewis
authors.forename: H
authors.initials: H
authors.lastname: Chikumi
authors.forename: J S
authors.initials: JS
authors.lastname: Gutkind
authors.forename: Z S
authors.initials: ZS
authors.lastname: Derewenda
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D000939:Epitopes; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000737:chemistry / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017510:Protein Folding; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism; D020710:RGS Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D020741:rho GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D000939:Epitopes; D008164:Luminescent Proteins; D011518:Proto-Oncogene Proteins; D020710:RGS Proteins; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; C498015:GNAI2 protein, human; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020741:rho GTP-Binding Proteins