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  • 1
    Publication Date: 1991-11-29
    Description: The three-dimensional structure of the activated state of glycogen phosphorylase (GP) as induced by adenosine monophosphate (AMP) has been determined from crystals of pyridoxalpyrophosphoryl-GP. The same quaternary changes relative to the inactive conformation as those induced by phosphorylation are induced by AMP, although the two regulatory signals function through different local structural mechanisms. Moreover, previous descriptions of the phosphorylase active state have been extended by demonstrating that, on activation, the amino- and carboxyl-terminal domains of GP rotate apart by 5 degrees, thereby increasing access of substrates to the catalytic site. The structure also reveals previously unobserved interactions with the nucleotide that accounts for the specificity of the nucleotide binding site for AMP in preference to inosine monophosphate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sprang, S R -- Withers, S G -- Goldsmith, E J -- Fletterick, R J -- Madsen, N B -- R01 DK26081/DK/NIDDK NIH HHS/ -- R01 DK31507/DK/NIDDK NIH HHS/ -- New York, N.Y. -- Science. 1991 Nov 29;254(5036):1367-71.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas 75235-9050.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1962195" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Monophosphate/*pharmacology ; Amino Acid Sequence ; Binding Sites ; Enzyme Activation ; Macromolecular Substances ; Models, Molecular ; Phosphorylase b/chemistry/*metabolism ; Protein Conformation ; Pyridoxal Phosphate/analogs & derivatives/metabolism ; X-Ray Diffraction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1994-09-02
    Description: Mechanisms of guanosine triphosphate (GTP) hydrolysis by members of the G protein alpha subunit-p21ras superfamily of guanosine triphosphatases have been studied extensively but have not been well understood. High-resolution x-ray structures of the GTP gamma S and GDP.AlF4- complexes formed by the G protein Gi alpha 1 demonstrate specific roles in transition-state stabilization for two highly conserved residues. Glutamine204 (Gln61 in p21ras) stabilizes and orients the hydrolytic water in the trigonal-bipyramidal transition state. Arginine 178 stabilizes the negative charge at the equatorial oxygen atoms of the pentacoordinate phosphate intermediate. Conserved only in the G alpha family, this residue may account for the higher hydrolytic rate of G alpha proteins relative to those of the p21ras family members. The fold of Gi alpha 1 differs from that of the homologous Gt alpha subunit in the conformation of a helix-loop sequence located in the alpha-helical domain that is characteristic of these proteins; this site may participate in effector binding. The amino-terminal 33 residues are disordered in GTP gamma S-Gi alpha 1, suggesting a mechanism that may promote release of the beta gamma subunit complex when the alpha subunit is activated by GTP.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Coleman, D E -- Berghuis, A M -- Lee, E -- Linder, M E -- Gilman, A G -- Sprang, S R -- DK 46371/DK/NIDDK NIH HHS/ -- GM34497/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 2;265(5177):1405-12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Dallas, TX.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8073283" target="_blank"〉PubMed〈/a〉
    Keywords: Aluminum Compounds/metabolism ; Arginine/chemistry ; Binding Sites ; Catalysis ; Computer Graphics ; Crystallography, X-Ray ; Fluorides/metabolism ; GTP-Binding Proteins/*chemistry/metabolism ; Glutamine/chemistry ; Guanosine 5'-O-(3-Thiotriphosphate)/metabolism ; Guanosine Diphosphate/metabolism ; Guanosine Triphosphate/*metabolism ; Helix-Loop-Helix Motifs ; Hydrogen Bonding ; Hydrolysis ; Models, Molecular ; *Protein Conformation ; Protein Structure, Secondary
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Location Call Number Expected Availability
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