1SYK:
reference: Crystal structure of the E230Q mutant of cAMP-dependent protein kinase reveals an unexpected apoenzyme conformation and an extended N-terminal A helix., Wu J, Yang J, Kannan N, Madhusudan, Xuong NH, Ten Eyck LF, Taylor SS, Protein Sci 2005 Nov;14(11):2871-9. PMID: 16253959

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