Document Detail


Mechanism for multiple-substrates recognition of alpha-aminoadipate aminotransferase from Thermus thermophilus.
MedLine Citation:
PMID:  18831049     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Alpha-aminoadipate aminotransferase (AAA-AT), a homolog of mammalian kynurenine aminotransferase II (Kat II), transfers an amino group to 2-oxoadipate to yield alpha-aminoadipate in lysine biosynthesis through the alpha-aminoadipate pathway in Thermus thermophilus. AAA-AT catalyzes transamination against various substrates, including AAA, glutamate, leucine, and aromatic amino acids. To elucidate the structural change for recognition of various substrates, we determined crystal structures of AAA-AT in four forms: with pyridoxal 5'-phosphate (PLP) (PLP complex), with PLP and leucine (PLP/Leu complex), with N-phosphopyridoxyl-leucine (PPL) (PPL complex), and with N-phosphopyridoxyl-alpha-aminoadipate (PPA) at 2.67, 2.26, 1.75, and 1.67 A resolution, respectively. The PLP complex is in an open state, whereas PLP/Leu, PPL, and PPA complexes are in closed states with maximal displacement (over 7 A) of the alpha2 helix and the beta1 strand in the small domain to cover the active site, indicating that conformational change is induced by substrate binding. In PPL and PLP/Leu complexes, several hydrophobic residues on the alpha2 helix recognize the hydrophobic side chain of the bound leucine moiety whereas, in the PPA complex, the alpha2 helix rotates to place the guanidium moiety of Arg23 on the helix at the appropriate position to interact with the carboxyl side chain of the AAA moiety. These results indicate that AAA-AT can recognize various kinds of substrates using the mobile alpha2 helix. The crystal structures and site-directed mutagenesis revealed that intersubunit-electrostatic interactions contribute to the elevated thermostability of this enzyme.
Authors:
Takeo Tomita; Tomoharu Miyagawa; Takashi Miyazaki; Shinya Fushinobu; Tomohisa Kuzuyama; Makoto Nishiyama
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Proteins     Volume:  75     ISSN:  1097-0134     ISO Abbreviation:  Proteins     Publication Date:  2009 May 
Date Detail:
Created Date:  2009-03-16     Completed Date:  2009-05-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8700181     Medline TA:  Proteins     Country:  United States    
Other Details:
Languages:  eng     Pagination:  348-59     Citation Subset:  IM    
Affiliation:
Biotechnology Research Center, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
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MeSH Terms
Descriptor/Qualifier:
2-Aminoadipate Transaminase / chemistry*,  genetics,  metabolism*
2-Aminoadipic Acid / analogs & derivatives,  chemistry,  metabolism
Enzyme Stability
Hot Temperature
Humans
Leucine / analogs & derivatives,  chemistry,  metabolism
Point Mutation
Protein Conformation
Pyridoxal Phosphate / analogs & derivatives,  chemistry,  metabolism
Structural Homology, Protein
Substrate Specificity
Thermus thermophilus / enzymology*
Transaminases / chemistry,  metabolism
Chemical
Reg. No./Substance:
0/N-phosphopyridoxyl-alpha-aminoadipate; 0/N-phosphopyridoxylleucine; 54-47-7/Pyridoxal Phosphate; 542-32-5/2-Aminoadipic Acid; 61-90-5/Leucine; EC 2.6.1.-/Transaminases; EC 2.6.1.39/2-Aminoadipate Transaminase; EC 2.6.1.7/kynurenine-oxoglutarate transaminase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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