Algal [Fe]-hydrogenases also share the following characteristic
features (Fig. 1): (a) an amino acid residue insertion
(eight residues in both S. obliquus and C. reinhardtii HydA1
and HydA2) upstream of the H-cluster motif 1 and (b) a
second amino acid insertion (16 residues in C. fusca,
16 residues in S. obliquus HydA1 and HydA2, 45 residues
in C. reinhardtii HydA1, and 54 residues in C. reinhardtii
HydA2) between H-cluster motifs 2 and 3.