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Conformational Variation Revealed by the Crystal Structure of Rnase U2A Complexed with Ca Ion and 2´-Adenylic Acid at 1.03 Å Resolution

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Asparagine can be non-enzymatically deamidated and isomerized via succinimide to isoaspartate. This posttranslational modification can potentially alter the physical properties or the function of the parent protein. Asn32 of ribonuclease U2A from Ustilago sphaerogena is known to rapidly deamidate and isomerize in alkaline conditions. The crystal structure of ribonuclease U2A complexed with 2´-adenylic acid and calcium ions was determined at 1.03 Å resolution. In this structure, the region from Asp29 to Asp37 winds around a calcium ion, and the main-chain of Asn32-Gly33 adopts an extended conformation. Rotation of the side-chain of Asn32 could bring Asn32Cγ into close proximity to Gly33N, in a conformation suitable for succinimide formation. The structure suggests that in solution the region around Asn32-Gly33 is likely to be in equilibrium between multiple conformers, with the deamidation of Asn32 proceeding when the region adopts an extended conformation.

Keywords: (2'-AMP); 2'-Adenylic Acid; Arg85; Asn32; Asn32Cγ; Asn32O1; Asp29; Asp29O1; Asp37; Asp37O; Asparagine; Asparagine deamidation; C2'-endo ribose pucker; Ca Ion; Glu62; His101; His41; Tyr39; Ustilago sphaerogena; Val30O; X-ray diffraction; adenosine 2'-adenylic acid; glycerol; glycosyl bond; isoAsp; isoaspartate; isomerization; polyethylene glycol; ribonuclease U2; ribonuclease U2A; succinimide

Document Type: Research Article

Publication date: December 1, 2010

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  • Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.

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