The MLH1 Protein


   The sequence of the MHL1 gene is used to create a complimentary strand of messenger RNA (mRNA). The RNA carries the same base pair sequence as the coding DNA. However, the messenger RNA strand is processed to make it ready for protein synthesis. Chunks of mRNA called introns are removed from the strand because their sequences to not pertain to the code needed to build the peptide chain. 
   Once the mRNA is processed it exists the nucleus at attaches to a ribosome. At the same time transfer RNA (tRNA) attaches to amino acids. The structure of a transfer RNA molecule is shown here. The green, anticodon arm contains 3 key nucleotides that will match up with the codons on the mRNA strand in the ribosome. The acceptor arm at the top of the tRNA is where amino acids attach. Each of the 20 amino acids can only attach to the tRNAs that will bind to their specific codon on the mRNA strand. 
 
     The tRNA brings the amino acids to the ribosome and attaches them to each other in the order dictated by the mRNA strand. The resulting string of amino acids is called a peptide. The peptide then fold in a specific shape based on the reactions between the amino acids, to form the MLH1 protein.

    Mutations in the DNA will be copied into every strand of mRNA which then dictates the peptide formation. This means that every protein made from the mutated gene will be incorrect. This explains how detrimental a DNA mutation cane be.
 

What is known about the protein structure and function? 
What types of mutations affect the protein?
 
DePauw University HNPCC Home Page
Next Topic:  Other Sources of Information

Created by:  April Bardes, Colin Connor, and Allison Niggemyer, Biology Department, DePauw University, Bios 354:  Molecular Genetics, Spring 1998.