A tribute to Howard Dalton and methane monooxygenase

This is a brief account of the scientific contribution of Professor Sir Howard Dalton FRS, who died in January 2008. It starts with his important study of the physiology of nitrogen-fixing bacteria, but concentrates on his work on methane oxidation. This started with the development of reliable assays for the methane monooxygenase, leading to the discovery of two types of enzyme, soluble and membrane-bound and their regulation by copper levels in the growth medium. His contribution to our understanding of the structure and function of these enzymes is then discussed and the review closes with a brief summary of our present knowledge of these important enzymes.