{PDOC51850} {PS51850; KARI_N} {PS51851; KARI_C} {BEGIN} ******************************************* * KARI N- and C-terminal domains profiles * ******************************************* Ketol-acid reductoisomerase (KARI; EC 1.1.1.86), also known as acetohydroxy acid isomeroreductase (AHIR or AHAIR), catalyzes the conversion of acetohydroxy acids into dihydroxy valerates in the second step of the biosynthetic pathway for the essential branched-chain amino acids valine, leucine, and isoleucine. KARI catalyzes an unusual two-step reaction consisting of an alkyl migration in which the substrate, either 2-acetolactate (AL) or 2-aceto-2-hydroxybutarate (AHB), is converted to 3-hydoxy-3-methyl-2- oxobutyrate or 3-hydoxy-3-methyl-2-pentatonate, followed by a NADPH-dependent reduction to give 2,3-dihydroxy-3-isovalerate or 2,3-dihydroxy-3- methylvalerate respectively [1,2,3,4,5,6]. KARI is present only in bacteria, fungi, and plants, but not in animals. KARIs are divided into two classes on the basis of sequence length and oligomerization state. Class I KARIs are ~340 amino acid residues in length and include all fungal KARIs, whereas class II KARIs are ~490 residues long and include all plant KARIs. Bacterial KARIs can be either class I or class II. KARIs are composed of two types of domains, an N-terminal Rossmann fold domain and one or two C-terminal knotted domains. Two intertwinned knotted domains are required for function, and in the short-chain or class I KARIs, each polypeptide chain has one knotted domain. As a result, dimerization of two monomers forms two complete KARI active sites. In the long-chain or class II KARIs, a duplication of the knotted domain has occurred and, as a result, the protein does not require dimerization to complete its active site [1,2,3,4,5,6]. The alpha/beta KARI N-terminal Rossmann fold domain consists of a nine- stranded mixed beta-sheet with flanking alpha-helices on both sides of the beta-sheet (see ) [1,2,3,4,5]. The alpha-helical KARI C-terminal knotted domain can be described as a six- helix core in which helices coil like cable threads around each other, thus forming a bundle (see ) [1,2,3,4,5]. The profiles we developed cover the entire KARI N- and C-terminal domains. -Sequences known to belong to this class detected by the profile: ALL. -Other sequence(s) detected in Swiss-Prot: NONE. -Sequences known to belong to this class detected by the profile: ALL. -Other sequence(s) detected in Swiss-Prot: NONE. -Last update: January 2018 / First entry. [ 1] Biou V., Dumas R., Cohen-Addad C., Douce R., Job D., Pebay-Peyroula E. "The crystal structure of plant acetohydroxy acid isomeroreductase complexed with NADPH, two magnesium ions and a herbicidal transition state analog determined at 1.65 A resolution." EMBO J. 16:3405-3415(1997). PubMed=9218783; DOI=10.1093/emboj/16.12.3405 [ 2] Dumas R., Biou V., Halgand F., Douce R., Duggleby R.G. "Enzymology, structure, and dynamics of acetohydroxy acid isomeroreductase." Acc. Chem. Res. 34:399-408(2001). PubMed=11352718 [ 3] Ahn H.J., Eom S.J., Yoon H.-J., Lee B.I., Cho H., Suh S.W. "Crystal structure of class I acetohydroxy acid isomeroreductase from Pseudomonas aeruginosa." J. Mol. Biol. 328:505-515(2003). PubMed=12691757 [ 4] Tyagi R., Duquerroy S., Navaza J., Guddat L.W., Duggleby R.G. "The crystal structure of a bacterial class II ketol-acid reductoisomerase: domain conservation and evolution." Protein Sci. 14:3089-3100(2005). PubMed=16322583; DOI=10.1110/ps.051791305 [ 5] Cahn J.K.B., Brinkmann-Chen S., Spatzal T., Wiig J.A., Buller A.R., Einsle O., Hu Y., Ribbe M.W., Arnold F.H. "Cofactor specificity motifs and the induced fit mechanism in class I ketol-acid reductoisomerases." Biochem. J. 468:475-484(2015). PubMed=25849365; DOI=10.1042/BJ20150183 [ 6] Cahn J.K.B., Brinkmann-Chen S., Buller A.R., Arnold F.H. "Artificial domain duplication replicates evolutionary history of ketol-acid reductoisomerases." Protein. Sci. 25:1241-1248(2016). PubMed=26644020; DOI=10.1002/pro.2852 -------------------------------------------------------------------------------- PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) License, see https://prosite.expasy.org/prosite_license.html -------------------------------------------------------------------------------- {END}