Fritz Lipmann

Bio: Fritz Lipmann is an academic researcher from Rockefeller University. The author has contributed to research in topics: Amino acid & Tyrocidine. The author has an hindex of 31, co-authored 80 publications receiving 3829 citations. Previous affiliations of Fritz Lipmann include Rockefeller Institute of Government.

Adenosine triphosphate-linked concentration of calcium ions in a particulate fraction of rabbit muscle

Abstract: ATPase and ATP-dependent calcium ion concentration was studied with a membrane fraction isolated from homogenized rabbit skeletal muscle by differential centrifugation. Electron micrographs of the fraction indicate that it consists mainly of resealed tubules and vesicles of the endoplasmic reticulum. The up-to-1400-fold concentration of calcium in this fraction might be explained by proposing the existence of an energy-requiring system for the transport of calcium ions into the tubules or vesicles.

Mechanism of Activation by Adenosine 3′:5′-Cyclic Monophosphate of a Protein Phosphokinase from Rabbit Reticulocytes

Abstract: Two protein phosphokinases (EC 2.7.1.37) were found to be present in rabbit reticulocytes. The two enzymes were separated by DEAE-cellulose chromatography and called kinases I and II. Adenosien 3′:5′-cyclic monophosphate stimulated the activity of both enzymes. However, the degree of stimulation was different and depended on the protein acceptor used. In the presence of adenosine 3′:5′-cyclic monophosphate, protein kinase I dissociated into two subunits: a subunit binding adenosine 3′:5′-cyclic monophosphate, and a catalytic subunit. The component binding the cyclic nucleotide appeared to act as an inhibitory protein, regulating the activity of the catalytic subunit. The mechanism of action of the cyclic nucleotide on kinase II appeared to be different from that of kinase I.

Genistein, a specific inhibitor of tyrosine-specific protein kinases.

Abstract: Tyrosine-specific protein kinase activity of the epidermal growth factor (EGF) receptor, pp60v-src and pp110gag-fes was inhibited in vitro by an isoflavone genistein. The inhibition was competitive with respect to ATP and noncompetitive to a phosphate acceptor, histone H2B. By contrast, genistein scarcely inhibited the enzyme activities of serine- and threonine-specific protein kinases such as cAMP-dependent protein kinase, phosphorylase kinase, and the Ca2+/phospholipid-dependent enzyme protein kinase C. When the effect of genistein on the phosphorylation of the EGF receptor was examined in cultured A431 cells, EGF-stimulated serine, threonine, and tyrosine phosphorylation was decreased. Phosphoamino acid analysis of total cell proteins revealed that genistein inhibited the EGF-stimulated increase in phosphotyrosine level in A431 cells.

Energy conservation in chemotrophic anaerobic bacteria.

Abstract: [This corrects the article on p. 100 in vol. 41.].

Calmodulin plays a pivotal role in cellular regulation

Abstract: The role of calcium ions (Ca2+) in cell function is beginning to be unraveled at the molecular level as a result of recent research on calcium-binding proteins and particularly on calmodulin. These proteins interact reversibly with Ca2+ to form a protein . Ca2+ complex, whose activity is regulated by the cellular flux of Ca2+. Many of the effects of Ca2+ appear to be exerted through calmodulin-regulated enzymes.

Basic Medical Research Award. The ubiquitin system.

Abstract: The selective degradation of many short-lived proteins in eukaryotic cells is carried out by the ubiquitin system. In this pathway, proteins are targeted for degradation by covalent ligation to ubiquitin, a highly conserved small protein. Ubiquitin-mediated degradation of regulatory proteins plays important roles in the control of numerous processes, including cell-cycle progression, signal transduction, transcriptional regulation, receptor down-regulation, and endocytosis. The ubiquitin system has been implicated in the immune response, development, and programmed cell death. Abnormalities in ubiquitin-mediated processes have been shown to cause pathological conditions, including malignant transformation. In this review we discuss recent information on functions and mechanisms of the ubiquitin system. Since the selectivity of protein degradation is determined mainly at the stage of ligation to ubiquitin, special attention is focused on what we know, and would like to know, about the mode of action of ubiquitin-protein ligation systems and about signals in proteins recognized by these systems.

Phosphoenolpyruvate:carbohydrate phosphotransferase systems of bacteria.

Abstract: Numerous gram-negative and gram-positive bacteria take up carbohydrates through the phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS). This system transports and phosphorylates carbohydrates at the expense of PEP and is the subject of this review. The PTS consists of two general proteins, enzyme I and HPr, and a number of carbohydrate-specific enzymes, the enzymes II. PTS proteins are phosphoproteins in which the phospho group is attached to either a histidine residue or, in a number of cases, a cysteine residue. After phosphorylation of enzyme I by PEP, the phospho group is transferred to HPr. The enzymes II are required for the transport of the carbohydrates across the membrane and the transfer of the phospho group from phospho-HPr to the carbohydrates. Biochemical, structural, and molecular genetic studies have shown that the various enzymes II have the same basic structure. Each enzyme II consists of domains for specific functions, e.g., binding of the carbohydrate or phosphorylation. Each enzyme II complex can consist of one to four different polypeptides. The enzymes II can be placed into at least four classes on the basis of sequence similarity. The genetics of the PTS is complex, and the expression of PTS proteins is intricately regulated because of the central roles of these proteins in nutrient acquisition. In addition to classical induction-repression mechanisms involving repressor and activator proteins, other types of regulation, such as antitermination, have been observed in some PTSs. Apart from their role in carbohydrate transport, PTS proteins are involved in chemotaxis toward PTS carbohydrates. Furthermore, the IIAGlc protein, part of the glucose-specific PTS, is a central regulatory protein which in its nonphosphorylated form can bind to and inhibit several non-PTS uptake systems and thus prevent entry of inducers. In its phosphorylated form, P-IIAGlc is involved in the activation of adenylate cyclase and thus in the regulation of gene expression. By sensing the presence of PTS carbohydrates in the medium and adjusting the phosphorylation state of IIAGlc, cells can adapt quickly to changing conditions in the environment. In gram-positive bacteria, it has been demonstrated that HPr can be phosphorylated by ATP on a serine residue and this modification may perform a regulatory function.