Connecting B to A

Looking back on the bioinformatic analysis of eukaryotic nitrile hydratases in Marron, Akam and Walker's PLOS One paper to be found here, I thought it would be interesting to look at the link between the two segments which are separate subunits in prokaryotic NHases.
I mocked up this model of where the link had to go from two prokaryotic subunits which had most similarity to the Monosiga brevicollis NHase. The dangling ends of the right hand side of the structure indicate where the linker has to go.

As the easiest to access, I chose to align the protein sequences suggested by the transcriptions of ESTs from the four organisms held within the Broad Institute's Origins of Multicellularity project, namely M. brevicollis, Thecamonas trahens, Salpingoeca rosetta and Sphaeroforma arctica. (NB order in alignment: MB, SR, TT and last SA)

As Marron's paper comments:
"This histidine-rich region is prominent in T. trahens (12 residues), S. arctica (11 residues) and M. brevicollis (17 residues), but shorter in [...] S. rosetta (2 residues)."
That seems quite a lot of variation with only M. brevicollis having a string of pure histidines. In contrast the sequences are around the metal binding segment are quite similar.

Aureococcus anophagefferens- another eukaryote with a nitrile hydratase alpha chain

Whilst combing the data for new versions of nitrile hydratases which might be worthy of investigation, I came across a protein in the eukaryote alga Aureococcus anophagefferens which looks hugely like the alpha chain of a cobalt centred nitrile hydratase. I havent spotted the beta chain in the genome yet, but it is interesting to see that it doesnt seem to share the single subunit pattern of NHase like Monosiga brevicollis or Salpingoeca.

This phytoplankton is behind algal blooms which give "brown tides" off the eastern seaboard of the USA. (Image of organism below from here)

Salpingoeca

There is another marine eukaryote which has single subunit NHase- it is Salpingoeca. If you CLUSTALW it against Monosiga, it looks pretty similar (B subunit comes before A subunit, plenty of stars and colons but not the big section of histidines on the link.)