2j9i: Difference between revisions

[[Image:2j9i.jpg|left|200px]]

'''LENGSIN IS A SURVIVOR OF AN ANCIENT FAMILY OF CLASS I GLUTAMINE SYNTHETASES IN EUKARYOTES THAT HAS UNDERGONE EVOLUTIONARY RE-ENGINEERING FOR A TISSUE-SPECIFIC ROLE IN THE VERTEBRATE EYE LENS.'''

Lengsin is a major protein of the vertebrate eye lens. It belongs to the hitherto purely prokaryotic GS I branch of the glutamine synthetase (GS) superfamily, but has no enzyme activity. Like the taxon-specific crystallins, Lengsin is the result of the recruitment of an ancient enzyme to a noncatalytic role in the vertebrate lens. Cryo-EM and modeling studies of Lengsin show a dodecamer structure with important similarities and differences with prokaryotic GS I structures. GS homology regions of Lengsin are well conserved, but the N-terminal domain shows evidence of dynamic evolutionary changes. Compared with birds and fish, most mammals have an additional exon corresponding to part of the N-terminal domain; however, in human, this is a nonfunctional pseudoexon. Genes related to Lengsin are also present in the sea urchin, suggesting that this branch of the GS I family, supplanted by GS II enzymes in vertebrates, has an ancient role in metazoans.

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May  4 08:33:24 2008''