Question

A reference peptide, MPSGCWR, is subject to inherited alterations. The following peptide sequences have been reported: MPStGCWR, MPSGx, MPSGCWlvtgx, MPSGr, MPSGCWgcwr. Express these mutations using the accepted nomenclature (M=amino acid position 1).

Answer 1

The question involves expressing mutations in a peptide using accepted nomenclature, referencing specific changes like substitutions, truncations, insertions, and duplications in the amino acid sequence caused by underlying genetic mutations.

Step-by-step explanation:

The question relates to how changes in the amino acid sequence of a peptide, due to mutations in the gene encoding it, are expressed using accepted nomenclature. Starting with our reference peptide MPSGCWR:

• MPStGCWR indicates a replacement where serine replaces threonine at position 4, denoted as S4T.
• MPSGx suggests a truncation after glycine at position 5, indicated as G5* or G5Ter (termination).
• MPSGCWlvtgx presents two types of changes: a six-amino-acid insertion after tryptophan at position 7, I7_LVTGXins, and a truncation represented by x (termination), if we assume x here also indicates a stop codon.
• MPSGr implies a substitution of arginine for cysteine at position 6, which is denoted as C6R.
• MPSGCWgcwr appears to have a duplication of the last three amino acids, noted as W7_CWRdup.

These mutations are a result of changes in the complementary DNA sequence that lead to alterations in the mRNA sequence transcribed, ultimately affecting the amino acid sequence encoded.