|Dr. Vernon Ingram (left) chats with Dr. Kenneth Bridges. Dr. Peter Thumfort, a member of Dr. Ingram's laboratory group, listens in.|
After obtaining his doctorate in organic chemistry at Birkbeck College in London, Ingram spent 2 years in the United States preparing and crystallizing proteins at the Rockefeller Institute and studying peptide chemistry at Yale. Max Perutz invited him to come to the MRC unit at the Cavendish Laboratory in 1952 in order to place heavy metal atoms in myoglobin and hemoglobin, to facilitate analysis of their crystal structures. Shortly before Ingram joined the laboratory, Anthony Ellison attempted unsuccessfully to show a in the crystal structure between normal and sickle hemoglobin. Ellison left samples of sickle hemoglobin in the laboratory after abandoning his project. Perutz and Francis Crick persuaded Ingram to turn his attention to sickle hemoglobin. Ingram was well prepared for the task. He had already published several papers on amino acid and peptide chemistry.
A few years earlier, Frederick Sanger, also at the Cavendish Laboratory, sequenced bovine insulin in a ground breaking set of experiments. The far greater size and complexity of hemoglobin prohibited the simple adoption of Sanger's methods. Ingram hit on the idea of digesting hemoglobin into shorter segments using trypsin. This enzyme cleaves proteins only at lysine or arginine residues. Tryptic digestion produced a limited number of peptides that were amenable to analysis.
Separation by either electrophoresis or paper chromatography of tryptic peptides from hemoglobins A and S revealed no apparent differences. However, when Ingram combined the two techniques, with chromatography run perpendicular to the direction of electrophoresis, a two-dimensional "fingerprint" emerged in which Hbs A and S were identical in all but one peptide. A year later, he showed that the abnormal peptide from sickle hemoglobin differed by only a single amino acid: valine instead of the glutamic acid found in Hb A. This experiment provided elegant and convincing proof of the one gene-one protein hypothesis of Beadle and Tatum. Furthermore, the identification of the structural abnormality of Hb S paved the way for understanding the molecular pathogenesis of sickle cell disease. A few years later, Ingram and a graduate student, John Hunt, determined the amino acid replacement in Hb C (glutamic acid to lysine, also a position ß-6).
In 1958, Ingram joined the Biochemistry Department at the Massachusetts Institute of Technology. He is one of a distinguished group of scientists at MIT who created one a world-renowned center of cell and molecular biology investigation. At MIT, Ingram continued to explore hemoglobin variants. He and a graduate student, Anthony Stretton, established that Hb A2 differed from Hb A at several sites, thus providing structural evidence for tandem globin genes. They developed a valid scheme for the evolution of globin genes and were the first to classify the thalassemias into a and b groupings. Their classic paper on thalassemia shows remarkable prescience. Ingram and Stretton proposed that reduction in globin chain synthesis could result either from a silent mutation in the structural gene or from a defect in neighboring DNA that regulates gene expression. Investigators twenty years later, using DNA restriction enzymes and other techniques that marked the advent of modern molecular biology, showed this indeed to be the case.
Despite a lifetime of accomplishments whose sum exceeds that of many
eminent investigators, Ingram remains unpretentious. He credits co-workers
as well as students when discussing his work. He sees himself simply as
a link in the chain of human discovery. By any objective measure, he has
been an important link, indeed.