Replication Fidelity & a Proline-Rich Domain

The article 'Unusual Mechanism Keeps Repair Protein Accurate', at the Science Daily website reports what is described as an unusual mechanism involved in accurate repair of DNA. The protein involved in the repair is called DNA polymerase lambda. It is but one of a group of proteins referred to as DNA polymerases.

Other proteins having repair functions have been analyzed. Some accomplish their mission due to their proof-reading regions and some are known to interact with other biochemicals to realize their function. However the protein in question apears unusual with respect to the part of it that accounts for its accuracy.

Zucai Suo, assistant professor of biochemistry and a researcher with the Ohio State University Comprehensive Cancer Center led the related study and stated: “DNA is constantly attacked and damaged by a variety of agents. The body must properly repair that damage, or it can lead to cell death or to cancer, birth defects and other diseases." Suo noted the existence of six families of DNA polymerases and the uniqueness of the mechanism associated with the polymerase studied.

There are four domains to the protein and the structure of three of them was familiar. The surprise was region two which was rich in the amino acid proline. No known function could be correlated to this proline-rich domain. This was the key to the repair accuracy. DNA needs to be replicated and needs to be replicated with great accuracy. Here was the clue as to how it is accomplished.

The details of the process remain to be fleshed out. The protein is still being studied to learn exactly how the proline-rich domain ensures replication fidelity.

The new information clearly reveals the advantage of a particular protein domain but its historic implications need not be trivialized with a selection dunnit analysis. At the very least a credible analysis of its origins would reference its function and the plausibility that DNA could have foregone it at some prior point in time.