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Biomedical subjects

M Jecht

Publications and source records attributed to M Jecht.

9 recordsLinked to original sources
PubMed2003

European Union diabetes indicators: fact or fiction?

Diabetes mellitus is one of the major causes of morbidity and mortality in EU/EFTA countries. Monitoring risk factors for diabetes and its complications will offer the possibility to evaluate the development in time as well as the influence of possible interventions. In this investigation a list with core and secondary indicators is proposed. Availability of these indicators and their data sources is discussed. An important variability of data sources is used in EU/EFTA countries, interfering with the comparability of the outcome. Further harmonisation as well as continuous evaluation of data sources will be necessary to provide reliable tools to monitor diabetes mellitus and its outcome on a routine basis.

Comorbidity↗
PubMed1999

Intrinsic signals for the assembly of hepatitis A virus particles. Role of structural proteins VP4 and 2A.

Capsid assembly is the final event of virus replication, and its understanding is pivotal for the design of empty capsid-based recombinant vaccines and drug delivery systems. Although the capsid structure of several members of the picornavirus family has been elucidated, little is known about the structural elements governing the assembly process that is tightly associated with proteolytic processing of the viral polyprotein. Among the picornaviruses, hepatitis A virus (HAV) is unique in that it contains VP1-2A as a structural component and the small structural protein VP4, which argues for an assembly pathway different from that proposed for other picornaviruses. Using a recombinant system we show here that proteolytic processing of the HAV capsid proteins' precursor P1-2A is independent of the terminal domains 2A and VP4 of the substrate. However, both terminal domains play distinct roles in the assembly of viral particles. 2A as part of P1-2A is a primary signal for the assembly of pentameric structures which only further aggregate to empty viral capsids when VP4 is present as the N terminus of the precursor. Particle formation in the hepatovirus genus is thus regulated by two intrinsic signals that are distinct from those described for other picornaviruses.

Animals↗
PubMed1998

Membrane permeability induced by hepatitis A virus proteins 2B and 2BC and proteolytic processing of HAV 2BC.

The ability to rearrange membranes is a unique feature of nonstructural proteins 2B, 2C, and 2BC of some picornaviruses. To analyze in detail membrane binding of the respective proteins of hepatitis A virus (HAV), they were transiently expressed in the vaccinia/T7 system, and their effect on membrane permeability was studied using beta-galactosidase as reporter. Although 2C had no effect, the significantly increased reporter activity observed in the extracellular space of 2B- and 2BC-expressing cells points to a specific effect of HAV proteins 2B and 2BC on membrane permeability. In biochemical fractionation studies, HAV 2C and 2BC showed properties of intregral membrane proteins, whereas 2B was associated with membranes as a peripheral protein. Proteinase 3C-mediated cleavage of precursor 2BC in vivo was most efficient when the enzyme was coexpressed in its precursor forms P3 or 3ABC, which both include the membrane-anchoring domain 3A. 3ABC showed the same solubility pattern as 2BC, suggesting that colocalization of 2BC and 3ABC might be required for the efficient liberation of 2B and 2C and occurs on membranes that have been proposed as the site of viral RNA replication.

3C Viral Proteases↗
PubMed1998

Membrane association and RNA binding of recombinant hepatitis A virus protein 2C.

The direct function of hepatitis A virus (HAV) protein 2C, a putative NTPase, is not known, yet genetic evidence obtained from chimeric viruses carrying the 2C genomic region of different HAV variants indicates that it plays a pivotal role in viral replication. In a first assessment of its potential function(s), membrane and RNA binding properties of HAV 2C were studied after expressing the protein in various recombinant systems. In contrast to poliovirus 2C, expression of HAV 2C was inhibitory to the growth and protein synthesis of bacteria. Deletion of the N-terminal amphipathic helix of 2C abrogated this effect and the ability of 2C to associate with eukaryotic membranes. Both, purified 2C and the N-terminally truncated protein were shown to bind RNA in vitro. Our data taken together suggest that HAV 2C is a multifunctional protein.

Animals↗
PubMed1998

Processing of proteinase precursors and their effect on hepatitis A virus particle formation.

Proteolytic processing of the picornaviral polyprotein mediated by the differential action of virus-encoded proteinase(s) is pivotal to both RNA genome replication and capsid formation. Possibly to enlarge the array of viral proteins, picornaviral polyprotein processing results in intermediate and mature products which apparently have distinct functions within the viral life cycle. For hepatitis A virus (HAV), we report here on the autoproteolysis of precursor polypeptides comprising the only viral proteinase, 3Cpro, and on their role in viral particle formation. Following transient expression of a nested set of 3Cpro-containing proteins (P3, 3ABC, 3BCD, 3CD, 3BC, and 3C) in eukaryotic cells, the extent of processing was determined by analyzing the cleavage products. The 3C/3D site was more efficiently cleaved than those at the 3A/3B and 3B/3C sites, leading to the accumulation of the intermediate product 3ABC. In the absence of 3A from the precursor, cleavage at the 3B/3C site was further reduced and a switch to an alternative 3C/3D site was observed. Coexpression of various parts of P3 with the precursor of the viral structural proteins P1-2A showed that all 3C-containing intermediates cleaved P1-2A with almost equal efficiency; however, viral particles carrying the neutralizing epitope form much more readily in the presence of the complete P3 domain than with parts of it. These data support the notion that efficient liberation of structural proteins from P1-2A is necessary but not sufficient for productive HAV capsid formation and suggest that the polypeptides flanking 3Cpro promote the assembly of viral particles.

Base Sequence↗
PubMed1997

Proteinase 3C-mediated processing of VP1-2A of two hepatitis A virus strains: in vivo evidence for cleavage at amino acid position 273/274 of VP1.

Two prominent features distinguish hepatitis A virus (HAV) from other members of the picornavirus family. A C-terminally prolonged precursor of the structural protein VP1 is incorporated into assembly intermediates (e.g., the provirion), and a single proteinase is contained within the HAV polyprotein. Using an in vivo expression system, we show that proteolytic liberation of VP1 from its precursors P1-2A and VP1-2A is catalyzed by the virus-encoded proteinase 3Cpro. Among the proposed cleavage sites within VP1-2A, the Glu/Ser pair found at VP1 amino acid position 273/274 of most HAV strains is efficiently processed, whereas proteolysis of the Val/Ser site of the attenuated HM175 strain is protracted. Two mutations within VP1-2A (Lys[297]Arg and Ser[330]Asn) had no effect on 3Cpro-mediated cleavage at this site. Additional sites in this region of VP1-2A can also be utilized as substrates by the proteinase, yet less efficiently, and might give rise to smaller and larger VP1 polypeptides also detected in HAV-infected cells.

3C Viral Proteases↗
PubMed1994

Autonomous folding of the excised coenzyme-binding domain of D-glyceraldehyde 3-phosphate dehydrogenase from Thermotoga maritima.

An important question in protein folding is whether compact substructures or domains are autonomous units of folding and assembly. The protomer of the tetrameric D-glyceraldehyde-3-phosphate dehydrogenase from the hyperthermophilic bacterium Thermotoga maritima has a complex coenzyme-binding domain, in which residues 1-146 form a compact substructure with the last 31 residues (313-333). Here it is shown that the gene of a single-chain protein can be expressed in Escherichia coli after deleting the 163 codons corresponding to the interspersed catalytic domain (150-312). The purified gene product is a soluble, monomeric protein that binds both NAD+ and NADH strongly and possesses the same unfolding transition induced by guanidinium chloride as the native tetramer. The autonomous folding of the coenzyme-binding domain has interesting implications for the folding, assembly, function, and evolution of the native enzyme.

Amino Acid Sequence↗