Structural and functional properties of lengsin, a pseudo-glutamine synthetase in the transparent human lens.
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Grassi F, Moretto N, Rivetti C, Cellai S, Betti M, Marquez AJ, Maraini G, Ottonello S
Structural and functional properties of lengsin, a pseudo-glutamine synthetase in the transparent human lens.
Biochem Biophys Res Commun. 2006 Nov 17;350(2):424-9. Epub 2006 Sep 25.
- PubMed ID
- 17010935 [ View in PubMed]
- Abstract
Lengsin (LGS) is an abundant transcript in the human lens, encoding a predicted polypeptide similar to glutamine synthetase (GS). We show that a major alternatively spliced product of LGS codes for a 57kDa polypeptide that assembles into a catalytically inactive dodecamer, cross-reacts with anti-GS antibodies, and is expressed at high levels in transparent, but not cataractous, human lenses. Based on this characteristic oligomeric organization, preferential expression in the transparent lens, and amyloid-beta association previously reported for GS, a potential chaperone-like role of LGS has been investigated. We find that LGS has six binding sites for the hydrophobic surface probe bis-ANS and relieves cellular toxicity caused by amyloid-beta expression in a folding-impaired yeast mutant. While documenting the structural similarity between LGS and prokaryotic GS-I, the data rule out any involvement of lengsin in glutamine biosynthesis and suggest an unrelated role that may be important for lens homeostasis and transparency.