Title : Glycosylation increases the thermostability of human
aquaporin 10 protein
Abstract :
- Human aquaporin10 ( hAQP10 ) is a transmembrane facilitator of both water and glycerol transport in the small intestine
- This aquaglyceroporin is located in the apical membrane of enterocytes and is believed to contribute to the passage of water and glycerol through these intestinal absorptive cells
- Here we overproduced hAQP10 in the yeast Pichia pastoris and observed that the protein is glycosylated at Asn-133 in the extracellular loop C
- This finding confirms one of three predicted glycosylation sites for hAQP10 , and its glycosylation is unique for the human aquaporins overproduced in this host
- Nonglycosylated protein was isolated using both glycan affinity chromatography and through mutating asparagine 133 to a glutamine
- All three forms of hAQP10 where found to facilitate the transport of water, glycerol, erythritol, and xylitol, and glycosylation had little effect on functionality
- In contrast, glycosylated hAQP10 showed increased thermostability of 3-6 °C compared with the nonglycosylated protein , suggesting a stabilizing effect of the N-linked glycan
- Because only one third of hAQP10 was glycosylated yet the thermostability titration was mono-modal, we suggest that the presence of at least one glycosylated protein within each tetramer is sufficient to convey an enhanced structural stability to the remaining hAQP10 protomers of the tetramer