A few amino acids are post-translationally removed from the C-terminal end of th

Question

A few amino acids are post-translationally removed from the C-terminal end of the beta-lactamase enzyme from B. imaginarium (i.e. after translation and release from the ribosome, a protease chews off a few amino acids). The pruified wildtype enzyme is 327 amino acids in length and the sequence of its C-terminal amino acids is shown below aligned with the C-terminal aminoa cids found in a mutant strain of B. imaginarium, which contains of a frameshift mutation that sbolishes processing if its C-terminus. This frameshift mutant has had its translational reading frame altered by insertion or deletion of a single nucleotide.

wild type: S N A K D W

mutant: S N A I R L D W Q M K

a. What was the mutational event that gave rise to the frameshift mutant? Determine precisely where the single nucleotide insertion or deletion occurred in the beta-lacatamase coding sequences.

b. What is the length of the wildtype enzyme prior to processing (how many amino acids)?

c. Deduce, as far as possible, the actual sequence of the C-terminus of the wild-type enzyme prior to processing.

Explanation / Answer

The C terminal sequence of the enzyme is given. It is processed and only few amino acids are left. In the case of mutant, frameshift mutation abolished processing of C-terminus sequence. a) The mutational event that gave rise to frame shift muatation, is involved with the proteases enzymes which will remove the amino acids in the wild type. It got effected in the mutant resulting in the abscence of processing. A single nucleotide deletion or insertion is not possible, and in this case deletion of 'K' amino acid is done and insertion of I, R, L took place. b) The number of amino acids that are present before the processing is 11 amino acids which are seen in the mutant due to absence of processing. c) The actual sequence of C-terminus before processing is S N A I R L K D W Q M K

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