Question

A population of cells is treated with a polypeptide hormone that induces mitosis, and the hormone's cell surface receptor is isolated after 15 minutes and subjected to fragmentation and mass spectrometry. Several of the peaks show a slight shift as compared to the same protein from cells not treated with the hormone. What is the most likely explanation of this phenomenon?

a) Phosphorylation of some amino acid residues
b) mRNA editing resulting in a slightly different amino acid sequence
c) Alternative exon usage
d) Proteolytic processing

Answer 1

The most likely explanation for the slight shift in peaks observed in the mass spectrometry analysis is phosphorylation of some amino acid residues.

Step-by-step explanation:

The most likely explanation for the slight shift in peaks observed in the mass spectrometry analysis of the isolated cell surface receptor after treatment with the polypeptide hormone is phosphorylation of some amino acid residues.

Binding of the hormone to the receptor likely activates protein kinases, which then phosphorylate specific amino acids in the receptor protein. This phosphorylation can cause a slight change in the mass of the receptor, leading to a shift in the peaks observed in the mass spectrometry analysis.

Phosphorylation of proteins is a common post-translational modification that can regulate protein function and signaling pathways in cells.