2mzb
From Proteopedia
Solution structural studies of GTP:adenosylcobinamide-phosphate guanylyltransferase (CobY) from Methanocaldococcus jannaschii
Structural highlights
Function[COBY_METJA] Guanylyltransferase that catalyzes the synthesis of adenosylcobinamide-GDP (AdoCbi-GDP) from adenosylcobinamide-phosphate (AdoCbi-P) and GTP. Is involved in adenosylcobalamin biosynthesis. Binds one GTP per dimer. Can not use other NTPs or GDP. Does not display AdoCbi kinase activity. Is also able to catalyze the condensation of 2-phospho-L-lactate (LP) with GTP in vitro to form PPi and (2S)-lactyl-2-diphospho-5'-guanosine (LPPG), but is much less efficient than CofC, the presumed enzyme catalyzing this reaction in vivo.[1] [2] Publication Abstract from PubMedGTP:adenosylcobinamide-phosphate (AdoCbi-P) guanylyl transferase (CobY) is an enzyme that transfers the GMP moiety of GTP to AdoCbi yielding AdoCbi-GDP in the late steps of the assembly of Ado-cobamides in archaea. The failure of repeated attempts to crystallize ligand-free (apo) CobY prompted us to explore its 3D structure by solution NMR spectroscopy. As reported here, the solution structure has a mixed alpha/beta fold consisting of seven beta-strands and five alpha-helices, which is very similar to a Rossmann fold. Titration of apo-CobY with GTP resulted in large changes in amide proton chemical shifts that indicated major structural perturbations upon complex formation. However, the CobY:GTP complex as followed by 1H-15N HSQC spectra was found to be unstable over time: GTP hydrolyzed and the protein converted slowly to a species with an NMR spectrum similar to that of apo-CobY. The variant CobYG153D, whose GTP complex was studied by X-ray crystallography, yielded NMR spectra similar to those of wild-type CobY in both its apo- state and in complex with GTP. The CobYG153D:GTP complex was also found to be unstable over time. Solution Structural Studies of GTP:Adenosylcobinamide-Phosphateguanylyl Transferase (CobY) from Methanocaldococcus jannaschii.,Singarapu KK, Otte MM, Tonelli M, Westler WM, Escalante-Semerena JC, Markley JL PLoS One. 2015 Oct 29;10(10):e0141297. doi: 10.1371/journal.pone.0141297., eCollection 2015. PMID:26513744[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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