Structural highlights
4oe5 is a 4 chain structure with sequence from Human. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
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| Ligands: | , |
| Related: | 4oe4, 4oe6 |
| Gene: | ALDH4, ALDH4A1, P5CDH (HUMAN) |
| Activity: | L-glutamate gamma-semialdehyde dehydrogenase, with EC number 1.2.1.88 |
| Resources: | FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT |
Disease
[AL4A1_HUMAN] Hyperprolinemia type 2. The disease is caused by mutations affecting the gene represented in this entry.
Function
[AL4A1_HUMAN] Irreversible conversion of delta-1-pyrroline-5-carboxylate (P5C), derived either from proline or ornithine, to glutamate. This is a necessary step in the pathway interconnecting the urea and tricarboxylic acid cycles. The preferred substrate is glutamic gamma-semialdehyde, other substrates include succinic, glutaric and adipic semialdehydes.[1]
Publication Abstract from PubMed
The proline catabolic enzyme Delta1-pyrroline-5-carboxylate dehydrogenase (ALDH4A1) catalyzes the NAD+-dependent oxidation of gamma-glutamate semialdehyde to l-glutamate. In Saccharomyces cerevisiae, ALDH4A1 is encoded by the PUT2 gene and known as Put2p. Here we report the steady-state kinetic parameters of the purified recombinant enzyme, two crystal structures of Put2p, and the determination of the oligomeric state and quaternary structure from small-angle X-ray scattering and sedimentation velocity. Using Delta1-pyrroline-5-carboxylate as the substrate, catalytic parameters kcat and Km were determined to be 1.5 s-1 and 104 muM, respectively, with a catalytic efficiency of 14000 M-1 s-1. Although Put2p exhibits the expected aldehyde dehydrogenase superfamily fold, a large portion of the active site is disordered in the crystal structure. Electron density for the 23-residue aldehyde substrate-binding loop is absent, implying substantial conformational flexibility in solution. We furthermore report a new crystal form of human ALDH4A1 (42% identical to Put2p) that also shows disorder in this loop. The crystal structures provide evidence of multiple active site conformations in the substrate-free form of the enzyme, which is consistent with a conformational selection mechanism of substrate binding. We also show that Put2p forms a trimer-of-dimers hexamer in solution. This result is unexpected because human ALDH4A1 is dimeric, whereas some bacterial ALDH4A1s are hexameric. Thus, global sequence identity and domain of life are poor predictors of the oligomeric states of ALDH4A1. Mutation of a single Trp residue that forms knob-in-hole interactions across the dimer-dimer interface abrogates hexamer formation, suggesting that this residue is the center of a protein-protein association hot spot.
Structural Studies of Yeast Delta-Pyrroline-5-carboxylate Dehydrogenase (ALDH4A1): Active Site Flexibility and Oligomeric State.,Pemberton TA, Srivastava D, Sanyal N, Henzl MT, Becker DF, Tanner JJ Biochemistry. 2014 Feb 17. PMID:24502590[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Srivastava D, Singh RK, Moxley MA, Henzl MT, Becker DF, Tanner JJ. The Three-Dimensional Structural Basis of Type II Hyperprolinemia. J Mol Biol. 2012 Apr 16. PMID:22516612 doi:10.1016/j.jmb.2012.04.010
- ↑ Pemberton TA, Srivastava D, Sanyal N, Henzl MT, Becker DF, Tanner JJ. Structural Studies of Yeast Delta-Pyrroline-5-carboxylate Dehydrogenase (ALDH4A1): Active Site Flexibility and Oligomeric State. Biochemistry. 2014 Feb 17. PMID:24502590 doi:http://dx.doi.org/10.1021/bi500048b
