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From Proteopedia

Introduction

The protein holds a vital role as a protein in the citric acid cycle. As a catalyst enzyme, aconitase facilitates the reaction that converts citrate to isocitrate, the product used by isocitrate dehydrogenase. It does this through its ability to form both a citrate and an isocitrate complex. This protein can be found both in the cytoplasm and mitochondria of multiple species, but in humans the cystolic form is utilized in the citric acid cycle.

Structural Features

The of aconitase contains both alpha helices (green) and beta sheets (blue) surrounding the ligands. The tertiary structure of the protein places its active site in the middle. Since aconitase exists as a monomer, no quaternary structure is present. are shown in brown throughout the protein's backbone. (light purple) are present throughout the secondary structure of aconitase, primarily in regions tucked close to the center of the protein. and charged residues(navy blue) are present in the protein in areas where it is typically exposed to water.

Ligand Interactions

Although its crystallization with water was unable to be shown here, aconitase exists surrounded by water molecules. Water is also able to access the active site of the protein, where it aids in the removal and addition of an OH group from the substrate. Several allow aconitase to form the citrate complex necessary for the citric acid cycle to occur. Looking at these it is easier to see the different components: the iron-sulfate complex (orange and yellow), citrate anion (red and gray), and oxygen atom (blue). The iron-sulfate complex helps the citrate anion to bind to the active site, which allow the protein to change conformation and form the isocitrate complex of aconitase. The (dark green) allow the enzyme to properly bind the ligand and perform the function. Ala642, Asp100, Asp165, Glu262, His101, His147, and His167 are the catalytic groups that allow aconitase to function effectively.