Allometric shape change and heterochrony in the freeliving coral Trachyphyllia bilobata (Duncan)

Regression analysis has been used to study the relationship between age, size, shape, and surface area in two ancestral-descendant populations of the Neogene Caribbean coral Trachyphyllia bilobata. Analyses of the relationship between size and age show that the relationship is isometric and that little difference occurs between populations in mean corallite length or height and in their rates of growth. Onset of columella growth is significantly earlier, however, in the descendant population. Studies of the relationship between size and shape show that growth is allometric, with shape change occurring in both corallum elongation and pinching of the corallite wall during ontogeny. In the descendant population, pinching and elongation initiate earlier in the ontogeny of the coral. These results suggest that the evolutionary development of the meandroid form in freeliving corals has been accomplished by heterochrony, involving a complex set of disassociated peramorphic changes in ontogeny accompanied by paedomorphic changes in astogeny. Further analyses show that the observed heterochronic changes serve to decrease corallum surface area which may in turn enhance sediment removal and nutrition in unstable habitats.     

Molybdenum cofactor deficiency in a patient previously characterized as deficient in sulfite oxidase

The metabolic status of a patient previously characterized as deficient in sulfite oxidase was reexamined applying new methodology which has been developed to distinguish between a defect specific to the sulfite oxidase protein and sulfite oxidase deficiency which arises as a result of molybdenum cofactor deficiency. Urothione, the metabolic degradation product of the molybdenum cofactor, was undetectable in urine samples from the patient. Analysis of molybdenum cofactor levels in fibroblasts by monitoring reconstitution of apo nitrate reductase in extracts of the Neurospora crassa mutant nit-1 revealed that cells from the patient were severely depleted. Quantitation of urinary oxypurines showed that hypoxanthine and xanthine were highly elevated while uric acid remained in the normal range. These results were interpreted to indicate a severe but incomplete deficiency of the molybdenum cofactor. The presence of very low levels of active cofactor, supporting the synthesis of low levels of active sulfite oxidase and xanthine dehydrogenase, could explain the metabolic patterns of sulfur and purine products and the relatively mild clinical symptoms in this individual.     

Receptor activation of G proteins

G proteins are a highly conserved family of membrane-associated proteins composed of alpha, beta, and gamma subunits. The alpha subunit, which is unique for each G protein, binds GDP or GTP. Receptors such as those for beta- and alpha-adrenergic catecholamines, muscarinic agonists, and the retinal photoreceptor rhodopsin, catalyze the exchange of GDP for GTP binding to the alpha subunit of a specific G protein. G alpha.GTP regulates appropriate effector enzymes such as adenylyl cyclase or the cyclic GMP phosphodiesterase. The beta gamma-subunit complex of G proteins is required for efficient receptor-catalyzed alpha subunit guanine nucleotide exchange and also functions as an attenuator of alpha subunit activation of effector enzymes. Recent elucidation of both receptor and G protein primary sequence has allowed structural predictions and new experimental approaches to study the mechanism of receptor-catalyzed G protein regulation of specific effector systems and the control of cell function including metabolism, secretion, and growth.     

Trimethylamine oxidation in liver tissue is not catalyzed by a molybdenum cofactor-dependent enzyme

The oxidation of trimethylamine to trimethylamine N-oxide in animals is catalyzed by an enzyme which has not yet been fully characterized. The discovery that a bacterial enzyme catalyzing the reverse reaction, the reduction of trimethylamine N-oxide to trimethylamine, utilizes the molybdenum cofactor to carry out this function raised the possibility that trimethylamine oxidation may also be dependent on this cofactor. It was found, however, that liver tissue from tungsten-treated rats contained normal levels of trimethylamine oxidase. In addition, analysis of a urine sample from a patient with trimethylamine oxidase deficiency revealed the presence of normal levels of urothione, the degradation product of the molybdenum cofactor. These results suggest that trimethylamine oxidase is not a molybdoenzyme and that oxidation of trimethylamine proceeds by a mechanism which differs considerably from a simple reversal of trimethylamine N-oxide reduction.     

Purification, characterization and antimicrobial spectrum of a bacteriocin produced by Pediococcus acidilactici

An antimicrobial peptide designated pediocin AcH was isolated from Pediococcus acidilactici strain H. The pediocin AcH was purified by ion exchange chromatography. The molecular weight of pediocin AcH was determined by SDS-PAGE to be about 2700 daltons. Pediocin AcH was sensitive to proteolytic enzymes, resistant to heat and organic solvents, and active over a wide range of pH. Pediocin AcH exhibited inhibition against several food spoilage bacteria and foodborne pathogens including Staphylococcus aureus, Clostridium perfringens and Listeria monocytogenes. It was bactericidal to sensitive cells and acted very rapidly. The bactericidal effect was not produced by either cell lysis or apparent loss of membrane permeability.     

Ubiquitin as a degradation signal.

For many short-lived eukaryotic proteins, conjugation to ubiquitin, yielding a multiubiquitin chain, is an obligatory pre-degradation step. The conjugated ubiquitin moieties function as a 'secondary' signal for degradation, in that their posttranslational coupling to a substrate protein is mediated by amino acid sequences of the substrate that act as a primary degradation signal. We report that the fusion protein ubiquitin--proline--beta-galactosidase (Ub-P-beta gal) is short-lived in the yeast Saccharomyces cerevisiae because its N-terminal ubiquitin moiety functions as an autonomous, primary degradation signal. This signal mediates the formation of a multiubiquitin chain linked to Lys48 of the N-terminal ubiquitin in Ub-P-beta gal. The degradation of Ub-P-beta gal is shown to require Ubc4, one of at least seven ubiquitin-conjugating enzymes in S.cerevisiae. Our findings provide the first direct evidence that a monoubiquitin moiety can function as an autonomous degradation signal. This generally applicable, cis-acting signal can be used to manipulate the in vivo half-lives of specific intracellular proteins.