prokaryote evolution and globin proteins

[Ken Kinman]

Brian and other Taxacomers,
       First I need to make a correction from my posts late last night.
Although some bacteria have homodimeric hemoglobins, apparently none are
known to be heterodimeric (so there would not have been different alpha and
beta chains).  I must have been more tired than I thought.
      However, all the other points I made are okay.  The article I was
reacting to can be found at his URL address:
http://starbulletin.com/2001/08/09/news/story5.html
     It is in reference to a paper published by Hou et al., 2001 (PNAS,
98:9353-9358).  I still predict that cyanobacterial globins will be the most
primitive, and I plan to study these sequences this winter once the
Gloeobacter genome is placed online.
      As for photosynthesis based on H2S rather than H2O, I believe it to be
a secondary development, and that most photoautotrophs have used water from
the beginning.  And for those of you who might be unaware of it, it has been
demonstrated that oxygenic photosynthesis only requires a single photosystem
(even though most forms now use the complicated system with both
photosystems I and II).

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