Crystallographic snapshots of metalloenzyme complexes involved in biological carbon dioxide sequestration

Abstract

The Wood‐Ljungdahl pathway in acetogenic bacteria involves nine enzymes working together to convert two molecules of carbon dioxide and coenzyme A into acetyl‐CoA, which can subsequently be assimilated as cell carbon or converted to other products such as acetate or ethanol or butanol, depending on the acetogenic strain. Harnessing the ability of acetogens to produce commercially useful multicarbon compounds from carbon dioxide has long been of interest to the biotechnology community. The Drennan laboratory, in collaboration with the Ragsdale group, has solved crystal structures of metalloenzymes of this pathway, both alone and in complex, in order to gain mechanistic insight into the chemistry involved in these remarkable transformations, as well as to understand the molecular movements that allow these enzymes to act in concert. From structures of carbon monoxide dehydrogenase in complex with acetyl‐CoA synthase, we have obtained molecular pictures indicating how a unique Ni‐Fe‐S cluster can carry out reduction of carbon dioxide. From structures of our methyltransferase complexes, we have visualized the molecular movements that must occur for one‐carbon units to be passed from enzyme to enzyme.