Cholera- and Anthrax-Like Toxins Are among Several New ADP-Ribosyltransferases

Chelt, a cholera-like toxin from Vibrio cholerae, and Certhrax, an anthrax-like toxin from Bacillus cereus, are among six new bacterial protein toxins we identified and characterized using in silico and cell-based techniques. We also uncovered medically relevant toxins from Mycobacterium avium and Enterococcus faecalis. We found agriculturally relevant toxins in Photorhabdus luminescens and Vibrio splendidus. These toxins belong to the ADP-ribosyltransferase family that has conserved structure despite low sequence identity. Therefore, our search for new toxins combined fold recognition with rules for filtering sequences – including a primary sequence pattern – to reduce reliance on sequence identity and identify toxins using structure. We used computers to build models and analyzed each new toxin to understand features including: structure, secretion, cell entry, activation, NAD+ substrate binding, intracellular target binding and the reaction mechanism. We confirmed activity using a yeast growth test. In this era where an expanding protein structure library complements abundant protein sequence data – and we need high-throughput validation – our approach provides insight into the newest toxin ADP-ribosyltransferases

Genetic characterization of Bordetella pertussis filamentous haemagglutinin: a protein processed from an unusually large precursor

The nucleotide sequence of the structural gene for filamentous haemagglutinin (FHA), fhaB, a crucial adherence factor for Bordetella perfussis, has been determined. Its 10774 nucleotides are far more than necessary to encode the 220kD biologically active, mature polypeptide product, suggesting a role for co‐or post‐translational processing. Fusion proteins derived from various portions of the fhaB open reading frame (ORF) were used to generate polyclonal antisera. Western immunoblot analysis of purified FHA and Bordetella sp. whole cell extracts with these antisera indicated that the 220kD product is encoded by the 5 portion of the ORF and that the smaller polypeptide species are breakdown products of this polypeptide. These data, as well as N‐terminal amino acid sequencing of the major polypeptide species, suggest a scheme for the proteolytic processing of an FHA precursor polypeptide. Copyright © 1990, Wiley Blackwell. All rights reserve

Le strategie di mercato delle farmacie on-line: una analisi empirica

Internet ha cambiato la società e l’economia. Per quanto riguarda la sanità, il web offre molte opportunità, ma è anche una fonte di rischi per i pazienti, data la scarsa regolamentazione. Questo lavoro presenta le strategie di mercato delle farmacie on-line (FO) circa la promozione, l’offerta e le politiche di prezzo. Le farmacie si differenziano per varietà del prodotto (brand o generico), qualità, quantità e target di paziente. Il vuoto legislativo creato dalla mancanza di una regolazione sovranazionale del commercio elettronico permette di offrire prodotti anche a pazienti che usano il farmaco senza consultare un medico (o contro il parere dello stesso). In questo caso, le FO chiedono un prezzo più alto, minimizzano gli effetti collaterali e praticano sconti elevati per l’acquisto di grandi quantitativi

Probing the structure-activity relationship of E.coli LT-A by site directed mutagenesis

Computer analysis of the crystallographic structure of the A subunit of Escherichia coli heat-labile toxin (LT) was used to predict residues involved in NAD binding, catalysis and toxicity. Following site-directed mutagenesis, the mutants obtained could be divided into three groups. The first group contained fully assembled, non-toxic new molecules containing mutations of single amino acids such as Val-53-->Glu or Asp, Ser-63-->Lys, Val-97-->Lys, Tyr-104-->Lys or Asp, and Ser-114-->Lys or Glu. This group also included mutations in amino acids such as Arg-7, Glu-110 and Glu-112 that were already known to be important for enzymatic activity. The second group was formed by mutations that caused the collapse or prevented the assembly of the A subunit: Leu-41-->Phe, Ala-45-->Tyr or Glu, Val-53-->Tyr, Val-60-->Gly, Ser-68-->Pro, His-70-->Pro, Val-97-->Tyr and Ser-114-->Tyr. The third group contained those molecules that maintained a wild-type level of toxicity in spite of the mutations introduced: Arg-54-->Lys or Ala, Tyr-59-->Met, Ser-68-->Lys, Ala-72-->Arg, His or Asp and Arg-192-->Asn. The results provide a further understanding of the structure-function of the active site and new, non-toxic mutants that may be useful for the development of vaccines against diarrhoeal diseases