Prosite
Prosite is an online database which can be used to analyse protein function of a known amino acid sequence.
Prosite allows you to search using a particular sequence for protein motifs against those stored in the database, this information can then be used alongside other tools such as BLAST and SMART, to help determine the function of an uncharacterised protein [1].
Prosite can be accesed via http://www.ebi.ac.uk/Tools/ppsearch/