Editoral for Crystal Structure of Mn2+ bound Escherichia coli L-arabinose Isomerase (ECAI) : Implications in Protein Catalytic Mechanism and Thermo-Stability

Author:  Alexander Patananan

Institution:  UCLA
Date:  September 2007

The term protein originates from πρώτα, a Greek word meaning "prota" or "of primary importance." This word, although simple, illustrates an important fact - proteins are the workhorses of all living organisms. Although they seem at first glance to be simple bio-macromolecules composed of a combination of only 20 different amino acids, proteins exhibit an astonishing array of complexity and diversity. As catalysts, scaffolds, transporters, and regulators, these molecules are the building blocks of the organic robots we know as organisms.

Proteins are comprised of one or multiple versions of long chains of connected amino acids known as polypeptides. The human body alone has been estimated to have approximately two million proteins, and of all land based biological organisms, it is predicted that tens of millions of different proteins exist. Despite this, however, only about one million proteins have been documented to date, of which barely a fraction has been thoroughly analyzed. It is for this reason that the quality research performed by Cornell undergraduate student Weisha Zhu, and her advisors Babu Manjasetty and Mark R. Chance, is of such great importance.

Under the United States Department of Energy's Student Undergraduate Laboratory Internship, Weisha Zhu studied L-arabinose isomerise (ECAI), an enzyme found in Escherichia coli, at the Brookhaven National Laboratory (BNL). ECAI is an important enzyme because it is involved in the initial reactions of L-arabinose catabolism. The functional properties of proteins depend on the proteins three dimensional shapes. Protein structures can be determined by X-ray crystallography as a tool. The three dimensional structure of the apo form of Escherichia coli L-arabinose isomerase also plays a critical role in catalyzing the in vitro conversion of galactose into tagatose. At BNL, Weisha Zhu and colleagues grew ECAI + Mn2 using the hanging drop vapour diffusion method and diffraction data was obtained. The final result was the solved structure of the enzyme and its placement into the Protein Data Bank. Overall, this paper serves as a perfect example of the identification and comparison of protein structures to determine their specific properties.