4r1t
Crystal structure of Petunia hydrida cinnamoyl-CoA reductase
Structural highlights
FunctionCCR1_PETHY Involved in the latter stages of lignin biosynthesis (PubMed:24985707). Catalyzes one of the last steps of monolignol biosynthesis, the conversion of cinnamoyl-CoAs into their corresponding cinnamaldehydes (PubMed:24985707, PubMed:25217505). Mediates the conversion of feruloyl CoA to coniferylaldehyde (PubMed:24985707, PubMed:25217505). Also active toward p-coumaroyl-CoA and sinapoyl-CoA (PubMed:24985707, PubMed:25217505). Involved in the production of floral volatile phenylpropanoids in flowers of fragrant cultivars (e.g. cv. Mitchell and cv. V26) from cinnamic acid, a common precursor with the anthocyanin biosynthesis pathway involved in flower pigmentation (PubMed:24985707).[1] [2] Publication Abstract from PubMedThe enzymes cinnamoyl-CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) catalyze the two key reduction reactions in the conversion of cinnamic acid derivatives into monolignol building blocks for lignin polymers in plant cell walls. Here, we describe detailed functional and structural analyses of CCRs from Medicago truncatula and Petunia hybrida and of an atypical CAD (CAD2) from M. truncatula. These enzymes are closely related members of the short-chain dehydrogenase/reductase (SDR) superfamily. Our structural studies support a reaction mechanism involving a canonical SDR catalytic triad in both CCR and CAD2 and an important role for an auxiliary cysteine unique to CCR. Site-directed mutants of CAD2 (Phe226Ala and Tyr136Phe) that enlarge the phenolic binding site result in a 4- to 10-fold increase in activity with sinapaldehyde, which in comparison to the smaller coumaraldehyde and coniferaldehyde substrates is disfavored by wild-type CAD2. This finding demonstrates the potential exploitation of rationally engineered forms of CCR and CAD2 for the targeted modification of monolignol composition in transgenic plants. Thermal denaturation measurements and structural comparisons of various liganded and unliganded forms of CCR and CAD2 highlight substantial conformational flexibility of these SDR enzymes, which plays an important role in the establishment of catalytically productive complexes of the enzymes with their NADPH and phenolic substrates. Structural Studies of Cinnamoyl-CoA Reductase and Cinnamyl-Alcohol Dehydrogenase, Key Enzymes of Monolignol Biosynthesis.,Pan H, Zhou R, Louie GV, Muhlemann JK, Bomati EK, Bowman ME, Dudareva N, Dixon RA, Noel JP, Wang X Plant Cell. 2014 Sep 12. pii: tpc.114.127399. PMID:25217505[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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