Madison Knapp, Minshik Jo, Courtney L Henthorn, Marley Brimberry, Andrew D Gnann, Daniel P Dowling, Jennifer Bridwell-Rabb
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引用次数: 0
Abstract
Chlorophyll (Chl) is one of Nature's most complex pigments to biosynthesize and derivatize. This pigment is vital for survival and also paradoxically toxic if overproduced or released from a protective protein scaffold. Therefore, along with the mass production of Chl, organisms also invest in mechanisms to control its degradation and recycling. One important enzyme that is involved in these latter processes is chlorophyllase. This enzyme is employed by numerous photosynthetic organisms to hydrolyze the phytol tail of Chl. Although traditionally thought to catalyze the first step of Chl degradation, recent work suggests that chlorophyllase is instead employed during times of abiotic stress or conditions that produce reactive oxygen species. However, the molecular details regarding how chlorophyllases are regulated to function under such conditions remain enigmatic. Here, we investigate the Arabidopsis thaliana chlorophyllase isoform AtCLH2 using site-directed mutagenesis, mass spectrometry, dynamic light scattering, size-exclusion multiangle light scattering, and both steady-state enzyme kinetic and thermal stability measurements. Through these experiments, we show that AtCLH2 exists as a monomer in solution and contains two disulfide bonds. One disulfide bond putatively maps to the active site, whereas the other links two N-terminal Cys residues together. These disulfide bonds are cleaved by chemical or chemical and protein-based reductants, respectively, and are integral to maintaining the activity, stability, and substrate scope of the enzyme. This work suggests that Cys residue oxidation in chlorophyllases is an emerging regulatory strategy for controlling the hydrolysis of Chl pigments.
期刊介绍:
ACS Bio & Med Chem Au is a broad scope open access journal which publishes short letters comprehensive articles reviews and perspectives in all aspects of biological and medicinal chemistry. Studies providing fundamental insights or describing novel syntheses as well as clinical or other applications-based work are welcomed.This broad scope includes experimental and theoretical studies on the chemical physical mechanistic and/or structural basis of biological or cell function in all domains of life. It encompasses the fields of chemical biology synthetic biology disease biology cell biology agriculture and food natural products research nucleic acid biology neuroscience structural biology and biophysics.The journal publishes studies that pertain to a broad range of medicinal chemistry including compound design and optimization biological evaluation molecular mechanistic understanding of drug delivery and drug delivery systems imaging agents and pharmacology and translational science of both small and large bioactive molecules. Novel computational cheminformatics and structural studies for the identification (or structure-activity relationship analysis) of bioactive molecules ligands and their targets are also welcome. The journal will consider computational studies applying established computational methods but only in combination with novel and original experimental data (e.g. in cases where new compounds have been designed and tested).Also included in the scope of the journal are articles relating to infectious diseases research on pathogens host-pathogen interactions therapeutics diagnostics vaccines drug-delivery systems and other biomedical technology development pertaining to infectious diseases.