2J9I:
reference: Lengsin is a survivor of an ancient family of class I glutamine synthetases re-engineered by evolution for a role in the vertebrate lens., Wyatt K, White HE, Wang L, Bateman OA, Slingsby C, Orlova EV, Wistow G, Structure. 2006 Dec;14(12):1823-34. PMID: 17161372

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