3w6s
From Proteopedia
yeast N-acetyltransferase Mpr1 involved in oxidative stress tolerance via proline metabolism
Structural highlights
FunctionMPR1_YEASX N-acetyltransferase involved in oxidative stress resistance. Acetylates the toxic proline metabolism intermediate (S)-1-pyrroline-5-carboxylate (P5C), or more likely its spontaneously forming tautomer glutamate-5-semialdehyde (GSA) into N-acetyl-GSA for arginine synthesis in the mitochondria. P5C has been shown to increase the levels of reactive oxigen species (ROS) in the cell by inhibiting the function of the respiratory chain in the mitochondria. The enzyme is able to reduce intracellular ROS levels under P5C-induced oxidative stress and protects cells from damage by oxidative stress (PubMed:15308773, PubMed:20550582, PubMed:22698729). Also acetylates and thereby detoxifies the proline analog azetidine-2-carboxylate (AZC), however it is unlikely that AZC is a natural substrate as it occurs only in plants belonging to the Lilaceae family (PubMed:11555637). Does not acetylate proline (PubMed:11555637, PubMed:12761200).[1] [2] [3] [4] [5] Publication Abstract from PubMedMpr1 (sigma1278b gene for proline-analog resistance 1), which was originally isolated as N-acetyltransferase detoxifying the proline analog l-azetidine-2-carboxylate, protects yeast cells from various oxidative stresses. Mpr1 mediates the l-proline and l-arginine metabolism by acetylating l-Delta1-pyrroline-5-carboxylate, leading to the l-arginine-dependent production of nitric oxide, which confers oxidative stress tolerance. Mpr1 belongs to the Gcn5-related N-acetyltransferase (GNAT) superfamily, but exhibits poor sequence homology with the GNAT enzymes and unique substrate specificity. Here, we present the X-ray crystal structure of Mpr1 and its complex with the substrate cis-4-hydroxy-l-proline at 1.9 and 2.3 A resolution, respectively. Mpr1 is folded into alpha/beta-structure with eight-stranded mixed beta-sheets and six alpha-helices. The substrate binds to Asn135 and the backbone amide of Asn172 and Leu173, and the predicted acetyl-CoA-binding site is located near the backbone amide of Phe138 and the side chain of Asn178. Alanine substitution of Asn178, which can interact with the sulfur of acetyl-CoA, caused a large reduction in the apparent kcat value. The replacement of Asn135 led to a remarkable increase in the apparent Km value. These results indicate that Asn178 and Asn135 play an important role in catalysis and substrate recognition, respectively. Such a catalytic mechanism has not been reported in the GNAT proteins. Importantly, the amino acid substitutions in these residues increased the l-Delta1-pyrroline-5-carboxylate level in yeast cells exposed to heat stress, indicating that these residues are also crucial for its physiological functions. These studies provide some benefits of Mpr1 applications, such as the breeding of industrial yeasts and the development of antifungal drugs. Structural and functional analysis of the yeast N-acetyltransferase Mpr1 involved in oxidative stress tolerance via proline metabolism.,Nasuno R, Hirano Y, Itoh T, Hakoshima T, Hibi T, Takagi H Proc Natl Acad Sci U S A. 2013 Jul 1. PMID:23818613[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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