Sandbox Reserved 192

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=='''Medical Implications'''==
=='''Medical Implications'''==
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Inhibition of Metastasis: A recent study published in 2010 discusses the possibility of using the degradation capabilities of RNase A and a similar protein DNase I to treat tumors. Tumor propagation is associated with an imbalance in nucleic acid degradation, which display themselves as increased levels of nucleic acids and decreased levels of nuclease activity in the blood of patients. The high levels of nucleic acids are caused by the unregulated expression and the secretion of a specific tumor-derived miRNA and DNA. It was found that the combined treatment of the RNase A and the DNase produced the best results by slowing the growth rate of the tumor. But both the ribonucleases are toxic at high levels; thus, only low levels can be administered to prevent adverse effects.
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''Inhibition of Metastasis'': A recent study published in 2010 discusses the possibility of using the degradation capabilities of RNase A and a similar protein DNase I to treat tumors. Tumor propagation is associated with an imbalance in nucleic acid degradation, which display themselves as increased levels of nucleic acids and decreased levels of nuclease activity in the blood of patients. The high levels of nucleic acids are caused by the unregulated expression and the secretion of a specific tumor-derived miRNA and DNA. It was found that the combined treatment of the RNase A and the DNase produced the best results by slowing the growth rate of the tumor. But both the ribonucleases are toxic at high levels; thus, only low levels can be administered to prevent adverse effects.

Revision as of 04:21, 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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Contents

Introduction

Ribonucleases or RNA depolymerases are ribosomes that catalyze RNA degradation in cells. They are most commonly found in the pancreas because they digest large amounts of RNA excreted by the stomach. The pancreas in ruminants, such as cows, have especially high amounts of ribonucleases in order to process nutrients from cellulose. One such ribonuclease, ribonuclease A or RNase A from cows, has been thoroughly studied due to its prevalence and structure.

Figure 1. This figure shows the three dimensional structure of RNase A

Drag the structure with the mouse to rotate


Structure

RNase A is made up of a single polypeptide chain of 124 residues. Of the 20 natural amino acids, RNase A possesses 19 of them, excluding tryptophan. This single polypeptide chain is cross-linked internally by four disulfide linkages, which contribute to the stability of RNase A. RNase A is in the shape of a kidney, with the active-site residues located within the cleft of the kidney. Active site residues and focus on it?? A long four-stranded anti-parallel ß-sheet and three short α-helices make up the secondary structure of RNase A. The amino acid sequence determines the three-dimensional structure of RNase A based on side-chain interactions.

History

RNase A has been used as a foundation enzyme for study. The 1972 Nobel Prize in Chemistry was awarded to three researchers for their work with RNase A on the folding of chains in RNase A and the stability of RNase A. By mutating the residues of RNase A by site-directed mutagenesis, the effects of these mutations were more visibly analyzed with advances in analytical chemistry instrumentation and techniques. RNase A was the first enzyme and third protein for which its amino acid sequence was correctly determined and the third enzyme and fourth protein whose three-dimensional structure was determined by X-ray diffraction analysis. NMR spectroscopy and Fourier transform infrared (FTIR) spectroscopy also was used with RNase A to describe protein structure and protein folding.

Medical Implications

Inhibition of Metastasis: A recent study published in 2010 discusses the possibility of using the degradation capabilities of RNase A and a similar protein DNase I to treat tumors. Tumor propagation is associated with an imbalance in nucleic acid degradation, which display themselves as increased levels of nucleic acids and decreased levels of nuclease activity in the blood of patients. The high levels of nucleic acids are caused by the unregulated expression and the secretion of a specific tumor-derived miRNA and DNA. It was found that the combined treatment of the RNase A and the DNase produced the best results by slowing the growth rate of the tumor. But both the ribonucleases are toxic at high levels; thus, only low levels can be administered to prevent adverse effects.

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