Mass spectrometry demonstrated that a bacterial protein and one section of a eukaryotic protein had amino acid sequences that were 90% similar. what else is likely to be true (but would still have to be tested experimentally)?

The similar sequences are regulated by the same interactions with other amino acids

Explanation:

If bacterial and eukaryotic proteins have 90% similarity in their amino acid sequences, it may mean that the genetic code of these two cells is extremely similar and, consequently, regulated by the same molecular interactions.

This is because the genetic code refers to the sequence of bases contained in a DNA that will correspond to amino acid sequences of the proteins created by that DNA. If two cells have a sequence of amino acids so similar, those cells probably have these sequences regulated by the same interactions with other amino acids.