Role of mitochondria in Parkinson disease.

The cause of the selective degeneration of nigrostriatal neurons in Parkinson disease (PD) has remained largely unknown. Exceptions include rare missense mutations in the alpha-synuclein gene on chromosome 4, a potentially pathogenic mutation affecting the ubiquitin pathway, and mutations in the parkin gene on chromosome 6. However, unlike classical PD, the latter syndrome is not associated with the formation of typical Lewy bodies. In contrast, a biochemical defect of complex I of the mitochondrial respiratory chain has been described in a relatively large group of confirmed PD cases. Recent cybrid studies indicate that the complex I defect in PD has a genetic cause and that it may arise from mutations in the mitochondrial DNA. Sequence analysis of the mitochondrial genome supports the view that mitochondrial point mutations are involved in PD pathogenesis. However, although mitochondria function as regulators in several known forms of cell death, their exact involvement in PD has remained unresolved. This is of relevance because classical apoptosis does not appear to play a major role in the degeneration of the parkinsonian nigra.

Comparison of three different recombinant hepatitis B virus core particles expressed in Escherichia coli.

The properties of three different recombinant hepatitis B virus core proteins expressed in Escherichia coli were compared: an N-terminal fusion protein, a C-terminally truncated protein and a sequence-authentic protein. All three proteins assembled into capsid-like particles with typical HBc-antigenicity, sedimentation behavior and distinctive electron microscopical images. Apart from this, however, variant HBc proteins displayed properties different from sequence-authentic HBc protein p21.4. Unlike p21.4, the particles of the N-terminal fusion protein p22.2 were sensitive to proteolytic attack by trypsin at variable sites within its arginine-rich C-terminus but not in its extended N-terminus. We therefore conclude that the C-terminal region is located on the surface of the p22.2 particle. These particles also showed increased HBe-antigenicity, as did the C-terminally truncated core particles p17.6, and to an even greater extent p18* particles which were derived from p22.2 by tryptic digestion. This might be interpreted as evidence for an--albeit minor--structural change. All variant core particles were less stable and contained less RNA. Electron microscopic indication for DNA binding of C-terminal deleted p17.6 particles was obtained using an aqueous spreading technique.

Expression of the core antigen gene of hepatitis B virus (HBV) in Acetobacter methanolicus using broad-host-range vectors.

Using the broad-host-range promoter probe vector pRS201 for cloning of phage Acm1 promoters, we established a convenient vector system for expression of heterologous genes in different Gram-negative bacteria. The usefulness of this system was demonstrated by expression of the HBV core gene in Acetobacter methanolicus. Plasmids carrying the HBV core gene downstream of different Acm1-phage promoters were transferred to A. methanolicus, a new potential host for recombinant DNA expression. Using enzyme immunoassay and immunoblot techniques, the amount and composition of core antigen produced in A. methanolicus were compared with that derived from Escherichia coli. The expression of immunoreactive core antigen in A. methanolicus exceeds by sevenfold that in E. coli using an expression system with tandemly arranged promoters. Morphological observations by electron microscopy show that the HBV core gene products isolated from both hosts are assembled into regular spherical particles with a diameter of about 28 nm that are comparable to original viral nucleocapsids.

[Comparison between alpha-amylase from B. amyloliquefaciens and B. licheniformis]. / Vergleich zweier alpha-Amylasen aus B. amyloliquefaciens und B. licheniformis.

Two sequence-homologous alpha-amylases from B. amyloliquefaciens and B. licheniformis were studied with respect to their stability against heat denaturation and were compared with respect to common structure-stabilizing principles. The investigated alpha-amylases were isolated from culture broth of B. amyloliquefaciens and B. licheniformis. The molecular parameters (molecular weight and isoelectric point) are similar. The thermostability was determined by changes of the protein structure (changes of the fluorescence emission spectra). At pH 5.0 the thermostable alpha-amylase from B. licheniformis showed a rate of denaturation which was achieved by the thermolabile alpha-amylase from B. amyloliquefaciens at a temperature 15 degrees lower. The alpha-amylase from B. licheniformis exhibits a marked stability also at the alkaline pH-range in contrast to the alpha-amylase from B. amyloliquefaciens. From measurements in the presence of EDTA and Ca2+ follows that both enzymes are stabilized by binding of calcium ions. An analysis of preferred amino acid exchanges between the two sequence-homologous alpha-amylases showed correspondences and differences to the well-known diagram of ARGOS. Possibly an increased thermic stability can already be achieved by special amino acid exchanges without significant changes in the protein structure.