If you only have protein sequences, you'll need to first perform a blast against swissprot database. Then, you take the best hit and fetch the uniprot id (id mapping tools from uniprot). To match coordinates of your protein with the one linked with the uniprot id the best is to perform an global pairwise alignment (see needle).
It would be smart to restrict your blast database to one species which would show the best annotation in terms of features...