Disease relevance of aqpZ

• Aquaporin water channel proteins are found throughout the plant and animal kingdoms, but the first prokaryotic water channel gene, aqpZ, was only recently identified in wild type Escherichia coli (Calamita G et al (1995) J Biol Chem 270, 29063-29066) [1].

High impact information on aqpZ

• When cocultured with parental wild-type E. coli, the aqpZ knockout mutant exhibits markedly reduced colony formation when grown at 39 degrees C. Similarly, the aqpZ knockout mutant also exhibits greatly reduced colony formation when grown at low osmolality, but this phenotype is reversed by overexpression of AqpZ protein [2].
• The molecular water transporter remained elusive until discovery of the Escherichia coli water channel, AqpZ, however the regulation of the aqpZ gene expression and physiological function of the AqpZ protein are unknown [2].
• Southern analysis failed to demonstrate aqpZ in mammalian genomic DNA, whereas a strongly reactive DNA was present in chromosomal DNA from Escherichia coli and other bacterial species and did not correspond to glpF [3].
• Expression of aqpZ cRNA conferred Xenopus oocytes with a 15-fold increase in osmotic water permeability, which was maximal after 5 days of expression, was not inhibited with HgCl2, exhibited a low activation energy (Ea = 3.8 kcal/mol), and failed to transport nonionic solutes such as urea and glycerol [3].
• When compared with other aquaporins, aqpZ encodes a 10-residue insert preceding exofacial loop C, truncated NH2 and COOH termini, and no cysteines at known mercury-sensitive sites [3].

Chemical compound and disease context of aqpZ

• Here we report expression of a histidine-tagged form of Escherichia coli aquaporin-Z (AqpZ) in its homologous expression system [4].
• The atomic structures of a transmembrane water plus glycerol conducting channel (GlpF), and now of aquaporin Z (AqpZ) from the same species, Escherichia coli, bring the total to three atomic resolution structures in the aquaporin (AQP) family [5].

Biological context of aqpZ

• Here we define the organization of aqpZ in E coli, produce the AqpZ protein and compare the AqpZ phylogeny to that of some known bacterial homologs [1].
• Physical mapping and sequence analyses confirmed the location of aqpZ at minute 19.7 on the E coli chromosome where it is transcribed counterclockwise [1].
• Striking similarities were found between the E coli aqpZ and a gene included in the genome of the cyanobacterium Synechocystis sp PCC6803, a species permanently living a fresh water [1].
• The aqpZ DNA isolated from E. coli contained a 693-base pair open reading frame encoding a polypeptide 28-38% identical to known aquaporins [3].
• The 8 A projection map of the AqpZ tetramer in frozen hydrated samples is similar to that of AQP1, consistent with the high sequence homology between these proteins [6].

Associations of aqpZ with chemical compounds

• Sucrose gradient sedimentation analysis showed that the native, solubilized AqpZ protein is a trypsin-resistant tetramer [4].
• This implies that single-file structure of the luminal water is more pronounced for AqpZ, the narrower channel of the two [7].

Analytical, diagnostic and therapeutic context of aqpZ

• Atomic force microscopy was used to image the surface of aquaporin Z, the water channel of Escherichia coli [8].
• Structure of the water channel AqpZ from Escherichia coli revealed by electron crystallography [6].

References