In recent years, many reports have appeared describing distinct heterogeneity of proteins that heretofore were considered to be a single species or type. The division of proteins into different classes or subtypes is aided by pharmacological tools such as selective ligands, functional measurements such as those examining kinetic or regulatory differences, and molecular biological approaches that have identified distinct genes coding for similar yet distinguishable gene products. Currently, much effort is directed toward understanding the significance of these sometimes subtle differences in terms of functional consequences for the cells in which they exist. Although most reports to date involve hormone and neurotransmitter receptor subtypes, it is also possible that other cell surface molecules such as ion transporters exist as multiple subtypes. In this paper we review the current evidence that Na(+)-H+ exchange activity is mediated by different Na(+)-H+ exchanger subtypes. Although subtypes have not been identified with certainty, we can predict certain distinguishing characteristics that these putative subtypes may have that may be of value in correlating predicted gene products obtained from cDNA cloning with previously characterized Na(+)-H+ exchangers.
The apicomplexan pathogen Eimeria causes coccidiosis, an intestinal disease of chickens, which has a major welfare and economic impact on the poultry industry. There is an urgent need to identify molecules that are rational targets for drug design and novel vaccines against coccidiosis. Apicomplexan secretory organelles, including micronemes and rhoptries, are essential for invasion of the host intestinal epithelium and establishment of parasitism. However, relatively little is known about the precise molecular function of these organelles, partly because few organelle proteins have been characterized. In this study, proteomics tools have been harnessed to define the protein repertoire of micronemes. Purified microneme proteins from Eimeria tenella sporozoites were excised from two-dimensional (2-D) gels and analyzed using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) and chemically assisted fragmentation (CAF)-MALDI with de novo sequencing. Peptide mass profiles were searched against the NCBI non-redundant (nr) database and against Eimeria-specific databases using the Mascot search algorithm, resulting in the identification of 37 of 96 spots excised from the 2-D gels. In addition, we have found CAF-MALDI to be a useful adjunct for identifying proteins, without the need for tandem MS. This global approach to protein characterization will be vital to gain greater understanding of the processes involved in apicomplexan host cell invasion.
Rotavirus is a common cause of diarrhoea both in the community and in the hospital. Because of this, it may be difficult to determine whether crossinfection has occurred in the hospital, an important finding as review of hygienic techniques and ward closure may be indicated. We therefore investigated the use of Polyacrylamide gel electrophoresis (PAGE) of the rotavirus RNA genome as a means of distinguishing between rotavirus strains in order to assess its role in the evaluation of apparent hospital-acquired rotavirus diarrhoea. Suspected examples of hospital-acquired rotavirus gastroenteritis were studied on an infectious diseases ward and a general infant ward. PAGE analysis demonstrated that crossinfection had not occurred on the infectious diseases ward, even though this was indicated clinically; a single source outbreak involving 11 patients was confirmed on the general infant ward, as all cases showed an identical rotavirus electropherotype. Following ward closure an endemic rotavirus electropherotype was detected, which affected 17 patients over a 3-month period. Electrophoresis of rotavirus RNA is a useful and practical technique in the analysis of hospital-acquired gastroenteritis and can indicate appropriate clinical action.
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