Sir John Walker is an English chemist who shared the Nobel Prize for Chemistry in 1997 with American Chemist Paul D. Boyer, and a Danish scientist Jens C. Skou. Walker received his doctorate from the Sir William Dunn School of Pathology at Oxford in 1969. In 1974 he joined the University of Cambridge in the Medical Research Council (MRC) Laboratory of Molecular Biology, at the urging of biochemist Frederick Sanger, where his experiments came out with the explanation of the enzymatic process that creates adenosine triphosphate (ATP).
Walker analyzed the sequences of proteins and then uncovered details of the modified genetic code in mitochondria. In 1978, he began studying ATP synthase, an enzyme of inner mitochondrial membrane and determined the amino acid sequence of this enzyme. By 1994, Walker clarified the three-dimensional structure of the enzyme, which consists of the F0 protein portion embedded in the inner membrane and connected by a sort of protein stalk or shaft to the F1 protein portion located in the matrix of the organelle. Walker’s results of the systematic working of this protein was supported by Boyer’s “binding change mechanism,” which leads to changes in chemical affinity of synthase protein portions for ATP and its precursor molecules.
In 1998 Walker became director of the MRC Dunn Human Nutrition Unit, also at Cambridge, which became the Mitochondrial Biology Unit in 2009. Under Walker’s direction one group that studied ATP synthase and another that studied all of the proteins found in the mitochondrion. He was elected a fellow of the Royal Society (1995), he was knighted (1999), and was awarded the Society’s highest honor, the Copley Medal (2012).