Paul C. Anagnostopoulos
31st January 2007, 06:35 AM
Anfinsen's principle states that the three-dimensional folding of a protein is based solely on its amino acid sequence. It appears that yet another cell biology principle is oversimplified.
In the latest issue of Science, an article describes the discovery of proteins with the same amino acid sequence but variant functions. How can this be?
A single-point mutation that still codes for the same amino acid is called a silent single nucleotide polymorphism (SNP). It is "silent" because it has no affect on the final protein, and thus, according to Anfinsen, no affect on the protein's structure. However, it turns out that it can have an affect on the rate at which amino acids are added to the nascent protein by the ribosome. This is because some aminoacyl-transfer RNAs* are more common than others, and the ribosome works more quickly when the tRNAs are plentiful. The speed at which amino acids are added can have an affect on the folding of the protein, and so its final structure, and so its function.
Beware the simplistic cell biology principle!
~~ Paul
* An aminoacyl-transfer RNA (tRNA) is a molecule that matches a codon triplet at one end and carries an amino acid at the other. These deliver amino acids to the ribosome and match up with the messenger RNA that codes the gene.
In the latest issue of Science, an article describes the discovery of proteins with the same amino acid sequence but variant functions. How can this be?
A single-point mutation that still codes for the same amino acid is called a silent single nucleotide polymorphism (SNP). It is "silent" because it has no affect on the final protein, and thus, according to Anfinsen, no affect on the protein's structure. However, it turns out that it can have an affect on the rate at which amino acids are added to the nascent protein by the ribosome. This is because some aminoacyl-transfer RNAs* are more common than others, and the ribosome works more quickly when the tRNAs are plentiful. The speed at which amino acids are added can have an affect on the folding of the protein, and so its final structure, and so its function.
Beware the simplistic cell biology principle!
~~ Paul
* An aminoacyl-transfer RNA (tRNA) is a molecule that matches a codon triplet at one end and carries an amino acid at the other. These deliver amino acids to the ribosome and match up with the messenger RNA that codes the gene.