Crystal structure of a novel mid-gut procarboxypeptidase from the cotton pest Helicoverpa armigera.

The cotton bollworm Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is one of the most serious insect pests in Australia, India and China. The larva causes substantial economical losses to legume, fibre, cereal oilseed and vegetable crops. This pest has proven to be difficult to control by conventional means, mainly due to the development of pesticide resistance. We present here the 2.5 A crystal structure from the novel procarboxypeptidase (PCPAHa) found in the gut extracts from H. armigera larvae, the first one reported for an insect. This metalloprotease is synthesized as a zymogen of 46.6 kDa which, upon in vitro activation with Lys-C endoproteinase, yields a pro-segment of 91 residues and an active carboxypeptidase moiety of 318 residues. Both regions show a three-dimensional structure quite similar to the corresponding structures in mammalian digestive carboxypeptidases, the most relevant structural differences being located in the loops between conserved secondary structure elements, including the primary activation site. This activation site contains the motif (Ala)(5)Lys at the C terminus of the helix connecting the pro- and the carboxypeptidase domains. A remarkable feature of PCPAHa is the occurrence of the same (Ala)(6)Lys near the C terminus of the active enzyme. The presence of Ser255 in PCPAHa instead of Ile and Asp found in the pancreatic A and B forms, respectively, enlarges the S1' specificity pocket and influences the substrate preferences of the enzyme. The C-terminal tail of the leech carboxypeptidase inhibitor has been modelled into the PCPAHa active site to explore the substrate preferences and the enzymatic mechanism of this enzyme.     

Listeriosis in Sheep

A comparison was made between a hay fed group, consisting of 23 ewes, and a grass silage fed group of 22 ewes, all pregnant. Excretion of Listeria monocytogenes (Lm) in the faeces and milk, antibody titres in sera and whey and delayed hypersensitivity against Lm, and several blood components were determined. The animals had previously been exposed to Lm, and Lm was isolated from the faeces from several animals when the experiment started. No significant difference in number of excretors between the 2 groups was found during the experimental period. The haemagglutination titres in both sera and whey were low and on the same level in both groups. The titres were higher in animals with 1 foetus than in animals with more than 1 foetus. In the first part of the experimental period the silage group had a reduced number of lymphocytes, lower total serum protein values and higher serum iron values, compared with the hay group. The silage group also had a stronger delayed hypersensitivity reaction against Lm than the hay group, and in the silage group the reaction was significantly stronger in ewes with 3 or more foetuses than in ewes with 1 foetus. In conclusion, the combined effect of some of the changes found in animals fed grass silage may leave them more susceptible to infections.     

Further results on the survival of a gene represented in a founder population

This paper is concerned with gene survival in a population which may increase without density dependence according to a generalization of the Moran model for haploid individuals. A selective advantage to one allele and the possibility of differential reproductive rates are allowed. Simple conditions are given for ultimate homozygosity to be certain and for the possibility of ultimate polymorphism. The results complement and extend those of Heyde (1981, 1982).     

Validation of DNA methylation profiling in formalin-fixed paraffin-embedded samples using the Infinium HumanMethylation450 Microarray

A formalin-fixed paraffin-embedded (FFPE) sample usually yields highly degraded DNA, which limits the use of techniques requiring high-quality DNA, such as Infinium Methylation microarrays. To overcome this restriction, we have applied an FFPE restoration procedure consisting of DNA repair and ligation processes in a set of paired fresh-frozen (FF) and FFPE samples. We validated the FFPE results in comparison with matched FF samples, enabling us to use FFPE samples on the Infinium HumanMethylation450 Methylation array.