Sandbox Reserved 197
From Proteopedia
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== '''Folding''' == | == '''Folding''' == | ||
| - | There are features of every protein that directly or indirectly effect the folding of that protein. Several of these features have been identified in RNase A by the use of mutants of the native form. These mutations and the study of the kinetics and final structure show whether that particular feature is involved in the folding of the protein. One particular feature of RNase A is the presence of ''cis'' proline residues. In nature, most amino acids reside in a ''trans'' conformation. Due to their cyclic structure, prolines are more stable in a ''cis'' conformation. RNase A contains four proline residues, two reside in the "cis" conformation and two in the "trans" conformation. The <scene name='Sandbox_Reserved_197/ | + | There are features of every protein that directly or indirectly effect the folding of that protein. Several of these features have been identified in RNase A by the use of mutants of the native form. These mutations and the study of the kinetics and final structure show whether that particular feature is involved in the folding of the protein. One particular feature of RNase A is the presence of ''cis'' proline residues. In nature, most amino acids reside in a ''trans'' conformation. Due to their cyclic structure, prolines are more stable in a ''cis'' conformation. RNase A contains four proline residues, two reside in the "cis" conformation and two in the "trans" conformation. The <scene name='Sandbox_Reserved_197/Tyr92-pro93/1'>Tyr-92-Pro93</scene> peptide group of RNase A in its native state is found in the ''cis'' conformation. Despite a P93A mutation, a cis conformation still forms; this is an unlikely conformation for an alanine residue. Upon unfolding, Tyr92-Ala93 undergoes isomerization to form its favored "trans" conformation. This points to the fact that this "cis" bond formation is a key component to the protein structure of RNase A. |
Another important feature of the folding of RNase A is the presence of four disulfide bonds. These bonds contribute to the thermal stability and the rate of folding of RNase A. The residues involved in these linkages include Cys26-Cys84, Cys58-Cys110, Cys40-Cys95, and Cys65-Cys72. Cys26-Cys84 and Cys58-Cys110 create an interaction between an alpha-helix and a beta sheet. This connection is the main contributor to the thermodynamic stability. | Another important feature of the folding of RNase A is the presence of four disulfide bonds. These bonds contribute to the thermal stability and the rate of folding of RNase A. The residues involved in these linkages include Cys26-Cys84, Cys58-Cys110, Cys40-Cys95, and Cys65-Cys72. Cys26-Cys84 and Cys58-Cys110 create an interaction between an alpha-helix and a beta sheet. This connection is the main contributor to the thermodynamic stability. | ||
Revision as of 20:45, 29 March 2011
| This Sandbox is Reserved from Feb 02, 2011, through Jul 31, 2011 for use by the Biochemistry II class at the Butler University at Indianapolis, IN USA taught by R. Jeremy Johnson. This reservation includes Sandbox Reserved 191 through Sandbox Reserved 200. |
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Introduction
Ribonuclease A is an enzyme involved in catalyzing RNA degradation. The structure of RNase A has been determined through crystallization and FABMS. There are several features of its structure that are pertinent to its folding and function. The catalytic residues of RNase A include His12, His 119, and Lys41. The active site lies within its cleft. RNase A has eight cysteine residues present that form four disulfide linkages which contribute to the ordered structure that has been observed as well as the speed of folding. Another important aspect to folding is the presence of two cis proline residues. There are specific parts of a protein that are required for the folding structure.
Folding
There are features of every protein that directly or indirectly effect the folding of that protein. Several of these features have been identified in RNase A by the use of mutants of the native form. These mutations and the study of the kinetics and final structure show whether that particular feature is involved in the folding of the protein. One particular feature of RNase A is the presence of cis proline residues. In nature, most amino acids reside in a trans conformation. Due to their cyclic structure, prolines are more stable in a cis conformation. RNase A contains four proline residues, two reside in the "cis" conformation and two in the "trans" conformation. The peptide group of RNase A in its native state is found in the cis conformation. Despite a P93A mutation, a cis conformation still forms; this is an unlikely conformation for an alanine residue. Upon unfolding, Tyr92-Ala93 undergoes isomerization to form its favored "trans" conformation. This points to the fact that this "cis" bond formation is a key component to the protein structure of RNase A.
Another important feature of the folding of RNase A is the presence of four disulfide bonds. These bonds contribute to the thermal stability and the rate of folding of RNase A. The residues involved in these linkages include Cys26-Cys84, Cys58-Cys110, Cys40-Cys95, and Cys65-Cys72. Cys26-Cys84 and Cys58-Cys110 create an interaction between an alpha-helix and a beta sheet. This connection is the main contributor to the thermodynamic stability.
