Molecular cloning, overexpression and characterization of a novel water channel protein from Rhodobacter sphaeroides

Mustafa Erbakan, Yue Xiao Shen, Mariusz Grzelakowski, Peter J. Butler, Manish Kumar, Wayne R. Curtis

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


Aquaporins are highly selective water channel proteins integrated into plasma membranes of single cell organisms; plant roots and stromae; eye lenses, renal and red blood cells in vertebrates. To date, only a few microbial aquaporins have been characterized and their physiological importance is not well understood. Here we report on the cloning, expression and characterization of a novel aquaporin, RsAqpZ, from a purple photosynthetic bacterium, Rhodobacter sphaeroides ATCC 17023. The protein was expressed homologously at a high yield (∼20 mg/L culture) under anaerobic photoheterotrophic growth conditions. Stopped-flow light scattering experiments demonstrated its high water permeability (0.17±0.05 cm/s) and low energy of activation for water transport (2.93±0.60 kcal/mol) in reconstituted proteoliposomes at a protein to lipid ratio (w/w) of 0.04. We developed a fluorescence correlation spectroscopy based technique and utilized a fluorescent protein fusion of RsAqpZ, to estimate the single channel water permeability of RsAqpZ as 1.24 (±0.41) × 10-12 cm3/s or 4.17 (±1.38) × 1010 H2O molecules/s, which is among the highest single channel permeability reported for aquaporins. Towards application to water purification technologies, we also demonstrated functional incorporation of RsAqpZ in amphiphilic block copolymer membranes.

Original languageEnglish (US)
Article numbere86830
JournalPloS one
Issue number1
StatePublished - Jan 31 2014

All Science Journal Classification (ASJC) codes

  • General


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