RIBOSOME-BOUND Β-Galactosidase

Abstract

cells among the images under f of the vertices of tj +1 is exactly r + 1, it is easily verified that f(btjr+l) contains exactly two non-degenerate r-simplexes of opposite orientations, so that f(atjr+1) = 0 + degenerate r-simplexes. If the number is less than r + 1, there are no nondegenerate r-simplexes in f(bt j +1). Hence, the only cases in which f(btfr+l) $ 0, when degenerate r-simplexes are dropped, are, those in which the r + 2 vertices of tTr+l are mapped onto the r + 2 vertices of sr+'.Suppose that this happens for x of the tjT+' with orientation preserved and for y with orientation reversed. Then Ef(btTr+1) = (x -y)(sor + sir + Sr+1), and, as in the proof for the case n = 1, we infer that x -y = 1. This completes the proof. Considerable evidence has been accumulated to show that ribonucleoprotein particles (ribosomes) provide sites for protein synthesis in animal cells.' Studies of the incorporation of radioactive tracers by Escherichia coli also indicated that the ribosomes of bacteria are active in protein synthesis (McQuillen, Roberts, and Britten2). These authors showed that in growing bacteria, a quantity of material roughly equal to the protein synthesized in three seconds was transiently associated with the ribosomes before being released to the soluble protein fraction of the cell. Since the rate of protein synthesis in E. coli is about 0.02 per cent per second, 0.06 per cent of any partictlar protein might be expected to be found transiently associated with the ribosomes. A series of experiments was started to determine whether fl-galactosidase showed the same transient association with ribosomes as was indicated for proteins in general. The first experiments showed that a small fraction of the enzyme was bound to the ribosomes, and it is the purpose of the present paper to describe some of the properties of this ribosome-associated enzyme. Furthermore, the results suggest a general procedure for isolating specific ribosomes.Materials and Methods.-E. coli strains: Three strains of E. coli differing in their 8-galactosidase-synthesizing properties were used, namely ML 30 (inducible), ML 308 (constitutive), and W2214 (absolute negative).Growth conditions: Cells were grown at 37°C in a vigorously aerated synthetic medium (C) of the following composition: 2 g NH4Cl, 6 g Na2HPO4, 3 g KH2PO4, 3 g NaCl, 0.01 g Mg as MgCl2, 0.026 g S as Na2SO4, 900 ml H20, and 10 ml. of 10 per cent maltose.Enzyme induction and assay: Thiomethyl-,3-D-galactoside (TMG) or thioisopropyl-fl-D-galactoside (TIPG) at 5 X 10-4 M were used as inducers of ft-galactosidase synthesis. Assays of d-galactosidase on ribosomal preparations were performed with the following mixture buffered at pH 7.4; 0.0027 M ortho-nitrophenyl-P-D-galactoside (ONPG), 0.05 M NaCl, 0.01 M trishydroxymethylaminomethane

Enzymatic activity of the ribosome‐bound nascent polypeptide

“…The previous observations of the enzymatic [20][21][22][23] or immunological [24] activity of growing ribosome-bound fl-galactosidase can be explained by the presence of the free enzyme subunits associated with the nascent chain, since fl-galactosidase is known to be active as a tetramer. In contrast, the firefly luciferase is active as monomer.…”

Antigenic relatedness of the DNA polymerase of human breast cancer particles to the enzyme of the Mason-Pfizer monkey virus.

“…The fact that the enzyme-IgG complexes can express some activity is not a new phenomenon. Indeed, in some reported instances such complexes are fully active (21) and this property was used to develop a convenient immunoprecipitation of specific ribosomes carrying newly synthesized chains of specific proteins (22).…”

Activation and inhibition of phosphorylase kinase by monospecific antibodies against preparatively isolated alpha, beta and gamma subunits

“…However there have been a number of reports on enzyme activations e.g. ribosomebound [58] and defective [59] ,8-gdlactosidase, penecillinases [60 -621, ribonuclease [63] glutamate dehydrogenase [64] and phosphofructokinase [65].…”