Viroporins are a group of proteins that participate in several viral functions, including the promotion of release of viral particles from cells. These proteins also a¡ect cellular functions, including the cell vesicle system, glycoprotein tra⁄ck-ing and membrane permeability. Viroporins are not essential for the replication of viruses, but their presence enhances virus growth. Comprising some 60^120 amino acids, viroporins have a hydrophobic transmembrane domain that interacts with and expands the lipid bilayer. Some viroporins also contain other motifs, such as basic amino acid residues or a domain rich in aromatic amino acids that confers on the protein the ability to interact with the interfacial lipid bilayer. Viroporin oligomerization gives rise to hydrophilic pores at the membranes of virusinfected cells. As the list of known viroporins steadily grows, recent research e¡orts focus on deciphering the actions of the viroporins poliovirus 2B, alphavirus 6K, HIV-1 Vpu and in£u-enza virus M2. All these proteins can enhance the passage of ions and small molecules through membranes depending on their concentration gradient. Future work will lengthen the list of viroporins and will provide a deeper understanding of their mechanisms of action.

A number of polysaccharides showed good antiviral activity against several animal viruses. At 5 ,Lg/ml, carrageenan prevented the cell monolayer from destruction by herpes simplex virus type 1 (HSV-1) growth. virions into cells indicated that carrageenan had no effect on virus attachment or virus entry. Moreover, carrageenan did not block the early permeabilization of cells to the toxic protein alpha-sarcin. These results suggest that this sulfated polysaccharide inhibits a step in virus replication subsequent to viral internalization but prior to the onset of late viral protein synthesis.

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Infection of T lymphocytes by the human immunodeficiency virus causes drastic alterations in the intracellular cation content of the infected cells. The human immunodeficiency virus type 1 genome encodes several accessory proteins, including Vpu, an integral membrane protein that forms ion channels in planar lipid bilayers. The effect of Vpu on the permeability of the plasma membrane to several molecules has been analyzed. Expression of vpu in Escherichia coli cells increases membrane permeability to a number of molecules such as 2-nitrophenyl beta-D-galactopyranoside, uridine, the impermeable translation inhibitor hygromycin B, and lysozyme. In addition, transient expression of Vpu in eukaryotic COS cells enhances entry of charged molecules such as hygromycin B and neurobiotin into these cells. The effect of Vpu on cell membrane permeability resembles that reported for other membrane-active proteins from different animal viruses, including influenza M2, Semliki Forest virus 6K, and poliovirus 2B and 3A proteins.

The human immunodeficiency virus type 1 (HIV-1) Vpr protein is an attractive target for antiretroviral drug development. The conservation both of the structure along virus evolution and the amino acid sequence in viral isolates from patients underlines the importance of Vpr for the establishment and progression of HIV-1 disease. While its contribution to virus replication in dividing and non-dividing cells and to the pathogenesis of HIV-1 in many different cell types, both extracellular and intracellular forms, have been extensively studied, its precise mechanism of action nevertheless remains enigmatic. The present review discusses how the apparently multifaceted interplay between Vpr and host cells may be due to the impairment of basic metabolic pathways. Vpr protein modifies host cell energy metabolism, oxidative status, and proteasome function, all of which are likely conditioned by the concentration and multimerization of the protein. The characterization of Vpr domains along with new laboratory tools for the assessment of their function has become increasingly relevant in recent years. With these advances, it is conceivable that drug discovery efforts involving Vpr-targeted antiretrovirals will experience substantial growth in the coming years.

In this study, we used chemical, biochemical, and histological techniques to obtain information on cell membrane permeability and onion tissue integrity after high pressure and thermal processing. Because there was strong agreement between the various methods used, it is possible to implement something relatively simple, such as ion leakage, into routine quality assurance measurements to determine the severity of preservation methods and the shelf life of processed vegetables.

Advanced food processing methods that accomplish inactivation of microorganisms but minimize adverse thermal exposure are of great interest to the food industry. High pressure (HP) and pulsed electric field (PEF) processing are commercially applied to produce high quality fruit and vegetable products in the United States, Europe, and Japan. Both microbial and plant cell membranes are significantly altered following exposure to heat, HP, or PEF. Our research group sought to quantify the degree of damage to plant cell membranes that occurs as a result of exposure to heat, HP, or PEF, using the same analytical methods. In order to evaluate whether new advanced processing methods are superior to traditional thermal processing methods, it is necessary to compare them. In this review, we describe the existing state of knowledge related to effects of heat, HP, and PEF on both microbial and plant cells. The importance and relevance of compartmentalization in plant cells as it relates to fruit and vegetable quality is described and various methods for quantification of plant cell membrane integrity are discussed. These include electrolyte leakage, cell viability, and proton nuclear magnetic resonance (1H-NMR).

Carboxypeptidases expressed in the aleurone layer participate in the mobilization of endosperm storage proteins during cereal grain germination. The genes encoding these proteins are also expressed in the scutellum of germinating grains, but their function in this organ is not yet clear. We have analyzed the expression of a carboxypeptidase III (CPIII) gene in germinating wheat (Triticum aestivum L.) grains. CPIII transcripts accumulated transiently in the scutellum showing a maximum at 2-3 days after imbibition and were exclusively localized to the scutellar vascular tissue. The analysis of CPIII expression in developing shoots and roots from growing seedlings confirmed the localization of CPIII transcripts to differentiating vascular tissue. The TUNEL assay detected in situ nuclear DNA fragmentation in cells showing CPIII expression, indicating that they undergo programmed cell death. Relative RT-PCR analysis showed that the CPIII gene expressed at high level in aleurone cells is the one expressed in vegetative tissues, and allowed the use of this gene as a molecular marker of tracheary element differentiation in wheat seedlings. These results are indicative of the involvement of serine carboxypeptidases in programmed cell death during the development of the vascular tissue in wheat, a new role for these enzymes, besides the mobilization of starchy-endosperm proteins during germination.