gamma. protein specified by bacteriophage lambda: structure and inhibitory activity for the recBC enzyme of Escherichia coli

Journal Article · Wed Jan 01 04:00:00 EST 1975 · J. Biol. Chem.; (United States)

OSTI ID:5143486

Karu, A E; Sakaki, Y; Echols, H; Linn, S

The protein encoded by the gam gene of bacteriophage lambda (''..gamma.. protein'') is a specific inhibitor of the recBC enzyme of Escherichia coli. The lambda protein has been purified approximately 2,000-fold, and its structure and inhibitory activity have been characterized. It appears to be composed of two identical subunits of 16,500 daltons, inhibits all of the catalytic activities of the recBC enzyme with apparently equal efficiency, but has no effect upon any other E. coli or lambda-DNase tested. Inhibition does not occur unless recBC enzyme is exposed to ..gamma.. protein prior to reaction of the enzyme with DNA. The inhibitory activity is independent of temperature, and no catalytic activity has been detected that might fulfill the inhibitory function. It appears instead that the inhibition involves a stoichiometric, rather than a catalytic interaction between ..gamma.. protein and the enzyme. Reaction kinetics for the recBC enzyme inhibited by ..gamma.. protein show no anomalous properties--only a depressed rate. Inhibition is not competitive and does not appear to affect the enzyme's affinity for DNA. The enzyme remains inhibited after it is separated from ''excess'' ..gamma.. protein by gel filtration or sedimentation in a glycerol gradient, and inhibited enzyme has a reduced electrophoretic mobility compared to that of uninhibited enzyme. ..gamma.. Protein inhibits recBC enzyme which has been reconstituted from cell-free extracts by complementation in vitro, but at least one of the complementing factors present in extracts from recB/sup -/ cells does not by itself form a complex with ..gamma.. protein. The mechanism of inhibition and the implications of these results for lambda replication and recombination are discussed.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 5143486
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 250:18; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
BACTERIOPHAGES
BIOCHEMICAL REACTION KINETICS
CATALYSIS
DNA
DNA REPLICATION
ENZYME INHIBITORS
ENZYMES
ESCHERICHIA COLI
INHIBITION
KINETICS
METABOLISM
MICROORGANISMS
MUTATIONS
NUCLEIC ACID REPLICATION
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PARASITES
PROTEINS
REACTION KINETICS
SEPARATION PROCESSES
VIRUSES