Killing of bacterial spores by dodecylamine and its effects on spore inner membrane properties.

AIMS: The objective of this study was to determine the effects of Ca-dipicolinic acid (CaDPA), cortex-lytic enzymes (CLEs), the inner membrane (IM) CaDPA channel and coat on spore killing by dodecylamine. METHODS AND RESULTS: Bacillus subtilis spores, wild-type, CaDPA-less due to the absence of DPA synthase or the IM CaDPA channel, or lacking CLEs, were dodecylamine-treated and spore viability and vital staining were all determined. Dodecylamine killed intact wild-type and CaDPA-less B. subtilis spores similarly, and also killed intact Clostridiodes difficile spores ± CaDPA, with up to 99% killing with 1 mol l-1 dodecylamine in 4 h at 45°C with spores at ~108  ml-1 . Dodecylamine killing of decoated wild type and CLE-less B. subtilis spores was similar, but ~twofold faster than for intact spores, and much faster for decoated CaDPA-less spores, with ≥99% killing in 5 min. Propidium iodide stained intact spores ± CaDPA minimally, decoated CaDPA-replete spores or dodecylamine-killed CLE-less spores peripherally, and cores of decoated CaDPA-less spores and dodecylamine-killed intact spores with CLEs. The IM of some decoated CaDPA-less spores was greatly reorganized. CONCLUSIONS: Dodecylamine spore killing does not require CaDPA channels, CaDPA or CLEs. The lack of CaDPA in decoated spores allowed strong PI staining of the spore core, indicating loss of these spores IM permeability barrier. SIGNIFICANCE AND IMPACT OF THE STUDY: This work gives new information on killing bacterial spores by dodecylamine, and how spore IM's relative impermeability is maintained.

Human oligosaccharyltransferase: isolation, characterization, and the complete amino acid sequence of 50-kDa subunit.

Oligosaccharyltransferase (OT) catalyzes the glycosylation of asparagine residues in nascent polypeptides in the endoplasmic reticulum. In a previous communication we reported the purification and characterization of this enzyme from chicken oviduct. Here we describe the purification and sequence analysis of OT from human liver microsomes. Oligosaccharyltransferase copurified with three proteins designated 50-kDa, 65-I and 65-II based on their molecular weights by gel electrophoresis. The N-terminal sequence of the 50-kDa component was homologous to the 50-kDa subunit of avian OT. The N-terminal sequences of 65-I and 65-II were identical to the primary structures of human ribophorins I and II, respectively, predicted by cDNA sequencing. The complete amino acid sequence of the 50-kDa subunit of human OT was determined by chemical sequencing of peptides isolated from chemical and enzymatic digests. The 50-kDa subunit of human OT is 98% identical to its canine homolog, 93% identical to its avian homolog, and 25% identical to the beta subunit of yeast OT. These data indicate that structural features of oligosaccharyltransferase are conserved in all eukaryotes.

Characterization of the covalent cross-links of the active sites of amidinated cytochrome b5 and NADH:cytochrome b5 reductase.

Preparations of amidinated cytochrome b5 and cytochrome b5 reductase, cross-linked by using a soluble carbodiimide to promote the formation of covalent bonds between carboxyl groups of the hemeprotein and nucleophilic residues of the flavoprotein at the surfaces involved in protein-protein contacts during electron transfer, have been used to characterize the charge pair interactions that occur during electron transfer between the free proteins. Sequence analyses of tryptic, V8 protease-, and Asp-N protease-generated peptides show that the heme propionyl carboxyl group at the surface of the cytochrome forms an ester bond with Ser162 of the reductase, thus implicating Lys163 as the normal participant in ionic bonding between the active sites of the two proteins. Moreover, Lys41 and Lys125 directly form amide bonds with carboxyl residues on the active-site surface of the cytochrome. In the case of Lys41, this involves Glu52 and/or Glu60, and Glu47 and/or Glu48 for Lys125, again implicating these residues as the groups that form charge pairs during normal interactions between the active sites of the two proteins.

Complete covalent structure of 60-kDa esterase isolated from 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced rabbit liver microsomes.

The 60-kDa esterase was isolated from liver microsomes of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced rabbits and its complete amino acid sequence determined. Automated sequence analysis of intact protein, as well as characterization of the peptides obtained from enzymatic and chemical cleavages, led to the elucidation of the primary structure. The protein is a single polypeptide consisting of 539 residues and molecular weight 59,478. The active site serine is 195, and another diisopropylphospho binding site is at histidyl 441. Carbohydrate chains are attached at aspariginyl residues 61 and 363. Although 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment induces this esterase severalfold, the amino acid sequence of the induced enzyme is identical to that of the enzyme isolated from liver microsomes of untreated rabbits. The sequence of the microsomal esterase is 30% identical with the sequences of human serum cholinesterase and the acetylcholinesterase from Torpedo californica. There is also a close homology between the 60-kDa esterase and the COOH-terminal domain of bovine thyroglobulin.