Protein splicing is a posttranslational autocatalytic process in which an intervening sequence, termed an intein, is removed from a host protein, the extein. Although we have a reasonable picture of the basic chemical steps in protein splicing, our knowledge of how these are catalyzed and regulated is less well developed. In the current study, a combination of NMR spectroscopy and segmental isotopic labeling has been used to study the structure of an active protein splicing precursor, corresponding to an N-extein fusion of the Mxe GyrA intein. The 1JNC coupling constant for the (1) scissile peptide bond at the N-extein–intein junction was found to be 12 Hz, which indicates that this amide is highly polarized, perhaps because of nonplanarity. Additional mutagenesis and NMR studies indicate that conserved box B histidine residue is essential for catalysis of the first step of splicing and for maintaining the (1) scissile bond in its unusual conformation. Overall, these studies support the ‘‘ground-state destabilization’’ model as part of the mechanism of catalysis.
Semisynthesis of a segmental isotopically labeled protein splicing precursor: NMR evidence for an unusual peptide bond at the N-extein-intein junction / Romanelli, Alessandra; A., Shekhtman; D., Cowburn; T. W. M. U. I., R.. - In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - ISSN 0027-8424. - STAMPA. - 101:17(2004), pp. 6397-6402. [10.1073/pnas.0306616101]
Semisynthesis of a segmental isotopically labeled protein splicing precursor: NMR evidence for an unusual peptide bond at the N-extein-intein junction
ROMANELLI, ALESSANDRA;
2004
Abstract
Protein splicing is a posttranslational autocatalytic process in which an intervening sequence, termed an intein, is removed from a host protein, the extein. Although we have a reasonable picture of the basic chemical steps in protein splicing, our knowledge of how these are catalyzed and regulated is less well developed. In the current study, a combination of NMR spectroscopy and segmental isotopic labeling has been used to study the structure of an active protein splicing precursor, corresponding to an N-extein fusion of the Mxe GyrA intein. The 1JNC coupling constant for the (1) scissile peptide bond at the N-extein–intein junction was found to be 12 Hz, which indicates that this amide is highly polarized, perhaps because of nonplanarity. Additional mutagenesis and NMR studies indicate that conserved box B histidine residue is essential for catalysis of the first step of splicing and for maintaining the (1) scissile bond in its unusual conformation. Overall, these studies support the ‘‘ground-state destabilization’’ model as part of the mechanism of catalysis.File | Dimensione | Formato | |
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