1JXB

I53A, a point mutant of the cysteine-free variant of E. coli Rnase HI

Summary for 1JXB

• Entry DOI: 10.2210/pdb1jxb/pdb
• Related: 1F21 1JL1
• Descriptor: Ribonuclease HI (2 entities in total)
• Functional Keywords: mixed alpha/beta, 4-helix bundle, hydrolase
• Biological source: Escherichia coli
• Cellular location: Cytoplasm (Potential): P0A7Y4
• Total number of polymer chains: 1
• Total formula weight: 17484.72

Authors

Spudich, G.,Lorenz, S.,Marqusee, S. (deposition date: 2001-09-06, release date: 2002-03-06, Last modification date: 2024-02-07)

Primary citation

Spudich, G.,Lorenz, S.,Marqusee, S.
Propagation of a single destabilizing mutation throughout the Escherichia coli ribonuclease HI native state.
Protein Sci., 11:522-528, 2002

PubMed Abstract: A point mutation (I53A) in the core of Escherichia coli RNase H* is known to destabilize both the native conformation (DeltaG(UN)) and the kinetic intermediate (DeltaG(UI)) by 2 kcal/mole. Here, we have used native-state hydrogen deuterium exchange to ask how this destabilization is propagated throughout the molecule. Stability parameters were obtained for individual residues in I53A and compared with those from the wild-type protein. A destabilization of 2 kcal/mole was observed in residues in the core but was not detected in the periphery of the molecule. These results are consistent with the localized destabilization of the core observed in the early intermediate of the kinetic folding pathway, supporting the resemblance of this kinetic intermediate to the partially unfolded form detected in the native state at equilibrium. A thermodynamic cycle also shows no interaction between Ile 53 and a residue in the periphery. There is, however, an increase in the number of denaturant-independent exchange events in the periphery of I53A, showing that effects of the point mutation are communicated to regions outside the core, although perhaps not through changes in stability. In sum, this work shows that localized regions within a protein can be destabilized independently. Furthermore, it implies a correspondence between the kinetic intermediate and the equilibrium PUF, as the magnitude and localization of the destabilization are the same in both.

PubMed: 11847275
DOI: 10.1110/ps.37202

Experimental method

X-RAY DIFFRACTION (1.6 Å)