Choline Oxidase

From Proteopedia

Revision as of 16:41, 8 December 2009

Abstract

Choline oxidase is the enzyme that catalyzes the reaction between choline and betaine glycine. Betaine glycine is an osmoprotectant and instrumental in helping plants and bacteria survive dry conditions. Studying the choline oxidase may help in the development of controlling populations of beneficial plants or pathogenic bacteria. The data was analyzed using the BLAST and Rasmol programs. The structure of choline oxidase from Arthrobacter globiformis (bacteria) was compared with the structure of the complimentary protein in Mus musculus (mice), carnitine acetyltransferase (Altschul et al., 2005). There are seven amino acids evolutionarily preserved within the vicinity of the flavin group (between amino acids 460 to 483 of each subunit). Of these seven, three are within 9 Å of the flavin group while the other four are farther away. These three are threonine 463, valine 464, and histadine 466. They are colored blue and are connected with the ligand via white monitor lines. The other four conserved residues are colored cyan, but are too far to really interact with the flavin group (colored cpk). Beta sheets are colored yellow to showcase the secondary structure of the entire subunit. Evolutionary preservation of the Thr463, may signify an importance in aiding the function of the flavin group as it relates to the activity of the enzyme. Previous studies indicate that His466 is indeed important in the function of choline oxidase (Quaye, Lountos, Fan, Orville, & Gadda, 2008).

RasMol Identification

The RasMol 2.6.5.1 was used to model choline oxidase and the seven evolutionarily preserved amino acids. For this to work, the model of choline oxidase was needed from the protein databank. This file was found, and saved, in the same folder as the RasMol program, as ‘2JBV.spt.’ It was opened in RasMol and the background was changed to white. One subunit of choline oxidase was restricted. The remaining plain subunit was given a backbone of 300 RasMol units and the wireframe of the amino acids residues was turned off. Each RasMol unit is 1/250 of an angstrom. The seven preserved amino acids and the flavin group were space filled with 275 RasMol units and wireframed with 225. The preserved residues were also highlighted in cyan. The three preserved residues closest to the FAD ligand were then changed to a blue color. Monitor lines were drawn between these three residues and the FAD prosthetic group, which was left in the original CPK color (see Figure 2). The monitor lines were colored white and spacefilled with 275 RasMol units. Beta sheets were colored yellow and highlighted the secondary structure of the molecule. Hydrogen bonds and more monitor lines were also added and colored white to support the model.

Works Cited

Altschul SF, Wootton JC, Gertz EM, Agarwala R, Morgulis A, Schäffer AA, and Yu YK (2005). Protein database searches using compositionally adjusted substitution matrices. FEBS J. 272, 5101-5109. Chen TH and Murata N. (2002). Enhancement of tolerance of abiotic stress by metabolic engineering of betaines and other compatible solutes. Curr. Opin. Plant Biol. 5, 250-257 Joosten V and van Berkel WJH. (2007). Flavoenzymes. Current Opinion in Chemical Biology, 11:195–202 ncbi.org. (2009). Retrieved November 20, 2009, from Protein Databank: www.ncbi.org Quaye, O., Lountos, G., Fan, F., Orville, A., & Gadda, G. (2008). Role of Glu312 in Binding and Positioning of the Substrate for the Hydride. Biochemistry, 47, 243-256. Rodwazowski KL, Khachatourians GG, and Selvaraj G. (1990). Choline oxidase, a catabolic enzyme in Arthrobacter pascens, facilitates adaptation to osmotic stress in Escherichia coli. J Bacteriol. 173(2), 472-478 Sakamoto A and Murata N. (2001). The Use of Bacterial Choline Oxidase, a Glycinebetaine – synthesizing Enzyme, to Create Stress-Resistant Transgenic Plants1. Plant Biology Vol. 125, pp. 180–188