Comparing 3D structures of a Fe-centred NHase and a Co-centred NHase

Using DeepView, I have used their "Iterative Magic Fit" to compare the AJ270 structure (Fe-centred) with the cobalt-centred structure reported as 3HHT by Van Wyk, Sewell, Cowan, Sayed, Tsekoa and Tastan Bishop.
The top picture shows how much homology there is between a cobalt centred NHase and an iron-centred NHase which I essentially chose at random [blue indicates similar, grading to yellow for dissimilar]. I have labelled the position of the metals in the centre of the overlayed proteins, and the text is unreadable because they fall on top of each other with this fit (which is based on aligning the carbon backbone)

The second picture is an attempt to show this metal-containing middle portion in greater detail.

This final picture above shows the 3D structure window and the primary sequence alignment window together. The lower sequence (Co-centred 3HHT) shows an extra section which isnt in the upper sequence (Fe-centred  AJ270), and corresponds to the alpha helix which is coloured yellow and lies roughly horizontally across the middle of the enzyme structure. This is a bit of structure which has been suggested as making a crucial difference in terms of extra stability.