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(non-oxygen transport proteins), the phylogeny of which has been extensively
studied ( Garrocho-Villegas, Gopalasubramaniam, & Arredondo-Peter, 2007;
Hoy, Robinson, et al., 2007; Vinogradov, Fernandez, et al., 2011 ). sHbs are
derived from one of two classes of nsHbs. Both the sHb and nsHb are part of
the M family of haemoglobins ( Vazquez-Limon et al., 2012 ).
Based upon previous analysis, the M family globins found in cyano-
bacteria and algae are typically represented by the SDgb class of globins,
and these globins do not seem to either exclude or imply the presence of
globins from the T lineage ( Vinogradov et al., 2013 ). Very few
M globins have been identified in cyanobacteria and green algae. With
one exception among Chlorophyta, these proteins are all SDgbs rather than
the chimeric FHbs ( Vinogradov, Fernandez, et al., 2011 ).
In the green algae, the T globins are more prevalent than the M (and S)
globins ( Vinogradov, Fernandez, et al., 2011 ). The M globins align well
with each other and relative to the cyanobacterial proteins as seen in
Fig. 6.4 . They also display strong similarity to the nsHbs found in land plants
(not shown). This suggests a common heritage for these globins and gives
strength to the theory that these 3/3 globins arose within Archaeplastida
via a single horizontal gene transfer event ( Vinogradov, Fernandez, et al.,
2011 ). This is mentioned because it is at odds with the results seen when
algae TrHbs are fit into the same tree, as discussed below. In connection with
the alignment of the M globins shown in Fig. 6.4 , it is interesting to note that
a structural homologue of the cyanobacterial 3/3 globins is Hell's Gate glo-
bin I, a haemoglobin from Methylacidiphilum infernorum (Verrucomicrobia
group). Hell's Gate globin I has been related to vertebrate neuroglobin
( Teh et al., 2011 ) and illustrates a key aspect of the evolution of
M globins ( Vinogradov, Hoogewijs, & Arredondo-Peter, 2011 ).
The phylogenetic tree drawn in Fig. 6.3 is clearly split into two different
branches. Based upon published sequence analysis of some of the proteins
found in the lower branch of the tree, these proteins should all contain a
canonical 3/3 fold and belong to the M family of globins (none of the
recently described SSDgbs were used to generate the figure). A small set
of six proteins from chlorophytes group together at the bottom of the tree,
showing the distinct evolutionary divergence of the eukaryotes from the
cyanobacteria. However,
these are still within the grouping for the
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