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G R Jacobson

Publications and source records attributed to G R Jacobson.

70 records · Page 4Linked to original sources
PubMed1976

Properties of a major protein released from Escherichia coli by osmotic shock.

A large fraction of a constitutively synthesized polypeptide, comprising 5% of the total Escherichia coli protein, is released when plasmolysed cells are subjected to osmotic shock into ice-cold water. Since the protein is not liberated by the conversion of cells to spheroplasts, it is not a typical periplasmic protein. A complex pattern of association with the cell envelope indicates that it is bound to this structure in vivo. Its susceptibility to trypsin and its interaction with specific antibodies vary with the type of preparations used. Based on these observations, we postulate a peripheral location at the inner surface of the plasma membrane. The protein has been purified to homogeneity from osmotic shock fluid. It has a mass of 44 000 daltons. Some of its physical and chemical properties have been investigated. Most remarkable are its strongly aggregating and adhesive characteristics and its precipitation by vinblastine and calcium ions. These unusual properties, its presumed location, and the observation that it is present in large amounts (approximately 70 000 molecules per cell) suggest a structural role for this protein.

Amino Acids↗
PubMed1976

Does a bacterial elongation factor share a common evolutionary ancestor with actin?

Protein synthesis elongation factor Tu from E. coli shares several physical, chemical, and functional properties with actin-like proteins. Limited tryptic degradation indicates that the two polypeptides have a similar molecular architecture. These observations suggest that they could have evolved from a common ancestor, although more information will be necessary to prove or disprove this hypothesis. A partial sequence, comprising 22 aminoacid residues from the aminoterminal end of the large tryptic fragment of elongation factor Tu is presented.

Actins↗
PubMed1976

ATP binding to a protease-resistant core of actin.

Actin can be cleaved by trypsin or chymotrypsin into a large, autonomous fragment with approximately 80% of the mass of the undegraded polypeptide. The protease-resistant cores obtained with either enzyme are very similar. Although the fragment does not bind calcium ions and fails to polymerize to the filamentous form of actin or to stimulate myosin adenosine triphosphatase (ATP phosphohydrolase, EC 3.6.1.3) activity, it retains the full capacity to bind ATP. This observation suggests that it represents an independent functional unit. Cleavage of globular actin with either trypsin or chymotrypsin occurs with half-times of 3 min, while that of filamentous actin proceeds with reaction half-times of 20 min for trypsin and nearly 2 hr for chymotrypsin. Denaturation and renaturation of the trypsin-resistant core shows that approximately 20% of the molecules refold to functional forms which indicates that the fragment can be considered as an independent unit of folding as well.

Actins↗
PubMed1976

Field dependence among male and female alcoholics: II. Norms for the rod-and-frame test.

402 males and 160 females hospitalized for treatment of alcoholism were tested in a standardized manner on the Rod-and-frame test as a means of supplementing an earlier report of normative data on perceptual style among male alcoholics. When their performance was contrasted with that of normal and psychiatric samples, alcoholics were clearly the most field dependent of all groups studied. Statistically significant sex differences justify the need for separate norms for males and females.

Adult↗
PubMed1975

Aspartate transcarbamylase of Escherichia coli. Mechanisms of inhibition and activation by dicarboxylic acids and other anions.

The interactions of several dicarboxylic acids and monoanions with Escherichia coli aspartate transcarbamylase and with its catalytic subunit have been studied by ultraviolet difference spectroscopy and steady state kinetics, with the following major findings. 1. A variety of dicarboxylic acids compete with carbamyl-P for the active sites of unliganded catalytic subunit, with steric requirements very different from those important for competition with L-aspartate for the subunit/carbamyl-P complex. Competition with carbamyl-P is much reduced if the dicarboxylic acid has a positively charged amino group. Acetate and chloride also compete. 2. At pH 7, equal concentrations of lysine acetate and L-aspartate are equally effective in displacing the transition state analog N-(phosphonacetyl)-L-aspartate (PALA) from the active sites of the concentrations of L-aspartate and lysine acetate is constant, increasing the concentration of L-aspartate does not relieve inhibition of the enzyme by PALA (Collins, K.C., and Stark, G. R. (1971) J. Biol. Chem. 246, 6599-6605). Therefore, the L-aspartate/subunit complex, like the acetate/subunit complex, must be incapable of participating in the catalytic reaction. We conclude that the kinetic mechanism is ordered, in agreement with the recent findings of Wedler and Gasser (Wedler, F.C., and Gasser, F.J. (1974), Arch. Biochem. Biophys. 163, 57-68) and in disagreement with the interpretation of Heyde et al. (Heyde, E., Nagabhushanam, A., And Morrison, J.F. (1973) Biochemistry 12, 4718-4726)...

Acetates↗
PubMedDate not supplied

Carbohydrate uptake in the oral pathogen Streptococcus mutans: mechanisms and regulation by protein phosphorylation.

Streptococcus mutans is the primary etiological agent of dental caries in man and other animals. This organism and other related oral streptococci use carbohydrates almost exclusively as carbon and energy sources, fermenting them primarily to lactic acid which initiates erosion of tooth surfaces. Investigations over the past decade have shown that the major uptake mechanism for most carbohydrates in S. mutans is the phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS), although non-PTS systems have also been identified for glucose and sucrose. Regulation of sugar uptake occurs by induction/repression and inducer exclusion mechanisms in S. mutans, but apparently not by inducer expulsion as is found in some other streptococci. In addition, ATP-dependent protein kinases have also been identified in S. mutans and other oral streptococci, and a regulatory function for at least one of these has been postulated. Among a number of proteins that are phosphorylated by these enzymes, the predominant soluble protein substrate is the general phospho-carrier protein of the PTS, HPr, as had previously been observed in a variety of Gram-positive bacteria. Recent results have provided evidence for a role for ATP-dependent phosphorylation of HPr in the coordination of sugar uptake and its catabolism in S. mutans. In this review, these results are summarized, and directions for future research in this area are discussed.

Carbohydrates↗