Question about potential chain of amino acids

The difficult amino acid is U, Selenocysteine, which is rare enough that it’s not really a reference that people would recognize.

But overall, the sequence is legit, though not naturally occurring in nature. Similar, real, sequences are "IAMSTARS" in the protein inositol kinase kinase (UvsB) from Talaromyces stipitatus and "MSTARDTWFF" in a PucR family transcriptional regulator from Segniliparus rotundus.

This quick search was done using NCBI Blast, software that compares a sequence of your choice against public sequence databases. (http://blast.ncbi.nlm.nih.gov/)

Best,
Chris