| Popis: |
The enzymological and purification data on acetylase, pointed out some of the difficulties in believing that acetylase was permease or part of it, but left it an open question. One of the first things to do was to get acetylase in pure form, find out how much was made in the cell, and measure its size. The surprise from the purification data was that there was very much less acetylase produced than β-galactosidase, 10 to 35 times less by weight, depending on conditions of growth. Acetylase was fairly straightforward. By physical and chemical studies it was clearly a dimer of two identical chains, each of about 30,000 daltons. Antibody to acetylase did not cross-react with β-galactosidase, nor with anything else in the cell. The subunit structure of β-galactosidase was a difficult problem. But when end-group and other studies were carried out, it became clear that β-galactosidase contains long, not short chains. In fact, the polypeptide contains 1,021 amino acids. β-Galactosidase has been a challenge, worthy of a lot of work. It still hasn’t lost its interest. There were and still are interesting mutants, as well as the structure to wonder about. Though acetylase was and is revisited from time to time, β-galactosidase has been the focus of attention in the author's lab for many years. |
