3k8z
From Proteopedia
Crystal Structure of Gudb1 a decryptified secondary glutamate dehydrogenase from B. subtilis
Structural highlights
Function[GUDB_BACSU] GudB seems to be intrinsically inactive, however spontaneous mutations removing a 9-bp direct repeat within the wild-type gudB sequence activated the GudB protein and allowed more-efficient utilization of amino acids of the glutamate family. This insertion presumably causes severe destabilization of the fold of the protein, leading to an inactive enzyme that is very quickly degraded. The cryptic GudB serves as a buffer that may compensate for mutations in the rocG gene and that can also be decryptified for the utilization of glutamate as a single carbon source in the absence of arginine. It is unable to synthesize glutamate.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAny signal transduction requires communication between a sensory component and an effector. Some enzymes engage in signal perception and transduction, as well as in catalysis, and these proteins are known as "trigger" enzymes. In this report, we detail the trigger properties of RocG, the glutamate dehydrogenase of Bacillus subtilis. RocG not only deaminates the key metabolite glutamate to form alpha-ketoglutarate but also interacts directly with GltC, a LysR-type transcription factor that regulates glutamate biosynthesis from alpha-ketoglutarate, thus linking the two metabolic pathways. We have isolated mutants of RocG that separate the two functions. Several mutations resulted in permanent inactivation of GltC as long as a source of glutamate was present. These RocG proteins have lost their ability to catabolize glutamate due to a strongly reduced affinity for glutamate. The second class of mutants is exemplified by the replacement of aspartate residue 122 by asparagine. This mutant protein has retained enzymatic activity but has lost the ability to control the activity of GltC. Crystal structures of glutamate dehydrogenases that permit a molecular explanation of the properties of the various mutants are presented. Specifically, we may propose that D122N replacement affects the surface of RocG. Our data provide evidence for a correlation between the enzymatic activity of RocG and its ability to inactivate GltC, and thus give insights into the mechanism that couples the enzymatic activity of a trigger enzyme to its regulatory function. Functional dissection of a trigger enzyme: mutations of the bacillus subtilis glutamate dehydrogenase RocG that affect differentially its catalytic activity and regulatory properties.,Gunka K, Newman JA, Commichau FM, Herzberg C, Rodrigues C, Hewitt L, Lewis RJ, Stulke J J Mol Biol. 2010 Jul 23;400(4):815-27. Epub 2010 May 31. PMID:20630473[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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