Affiliation:
1. Department of Biological Sciences, Columbia University, New York, New York 10027
Abstract
In a cell-free system, φ80d
lac
can be transcribed, and the resulting ribonucleic acid can be translated to yield a product which interacts with an enzymatically inactive
z
protein to produce active enzyme. The inactive
z
protein is produced by
Escherichia coli
strain 21, which contains a deletion in the first part of the gene for β-galactosidase and appears to exist as a dimer. The enzyme formed in the cell-free system appears to be composed of one strain 21
z
protein dimer and one newly synthesized polypeptide chain with a molecular weight of about 3 × 10
4
. The estimated size of this complementing segment is in good agreement with Ullmann, Jacob, and Monod's estimate of the size of the α region of β-galactosidase. Using α fragments produced by autoclaving or guanidine treatments, we found that the active portion of α seems to be smaller than the full α region. We also found, using α produced by the autoclaving technique, that active dimer undergoes conversion to tetramer as the amount of α is increased. Evidently, the binding of α favors this conversion, but it is unlikely that the conversion of dimer to tetramer per se results in increased enzyme activity.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
19 articles.
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