Hemoglobin and Chlorophyll

Bartosz Milewski said:

Is the similarity between hemoglobin and chlorophyll an accident or did one evolve from the other?

You should read Ross C. Hardison A brief history of hemoglobins: Plant, animal, protist, and
bacteria Proc. Natl. Acad. Sci. USA, Vol. 93, pp. 5675-5679, June 1996

pnas.org5675.pdfOpen ↗

It starts out: "The utility of metal-bound porphyrin rings for the transfer of electrons was
established early in evolution, as witnessed by the ubiquitous cytochromes that pass electrons down
an electrochemical gradient in the respiratory chain,..."

It continues: "Plants not only make oxygen during photosynthesis, but they also use it for
respiration through the electron transfer chain in mitochondria. Recent studies show that they use
hemoglobins to bind and transfer that oxygen."

So it shouldn't be surprising that the oxygen-binding, energy translating porphyrin ring should be
common to both plant and animal.

Of course, the heme group is different from the globin protein. The paper's Figure 1 outlines the
history of the hemoglobin gene.

On Sun, 1 Feb 2004 18:46:18 +0000 (UTC),

Bartosz Milewski said:

Is the similarity between hemoglobin and chlorophyll an accident or did one evolve from the other?

Hemoglobin consists of a protein (globin) and a heme group. Chlorophyll refers to a heme-like
molecule. The globin proteins are not even remotely related to the proteins that bind chlorophyll in
photosystems.

On the other hand, the heme in hemoglobin is structurally similar to the heme (chlorin) in
chlorohyll and to many other similar molecules in cytochromes etc.

The most primitive organisms must have had a pathway for porphyrin synthesis. Derivatives of these
porphyrins became part of cytochromes. Later on, there were additonal modifications of the porphyrin
pathway giving rise to what we now recognize as chlorophylls. Hemoglobin came several billion years
later but the heme porphyrin is basically the same as the cytochrome one.

Larry Moran

"Bartosz Milewski" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Is the similarity between hemoglobin and chlorophyll an accident or did one evolve from the other?

Presumably you mean the similarity between heme and chlorophyl. Hemoglobin is a protein that
carries heme.

Probably not an accident. There are other related biomolecules, including vitamin B12. It is not
clear (to me) which was first, if any. However, the words "evolve from" should be used carefully.
Heme didn't slowly become chlorophyl, if that is the direction that evolution took. Instead, the
heme production machinery evolved to become chlorophyl production machinery. At least that is a
better picture than saying that a small molecule evolved, even if the process went through
several steps.

Jim Menegay said:

"Bartosz Milewski" <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

Is the similarity between hemoglobin and chlorophyll an accident or did one evolve from the
other?

Presumably you mean the similarity between heme and chlorophyl. Hemoglobin is a protein that
carries heme.

Probably not an accident. There are other related biomolecules, including vitamin B12. It is not
clear (to me) which was first, if any. However, the words "evolve from" should be used carefully.
Heme didn't slowly become chlorophyl, if that is the direction that evolution took. Instead, the
heme production machinery evolved to become chlorophyl production machinery. At least that is a
better picture than saying that a small molecule evolved, even if the process went through
several steps.

Interesting distinction dont you think?

Did one metabolic protein slowly become another, or did the specific mechanisms of DNA facilitate
the process of evolution?

Hmmm - hypercycles are too tricky for my brain....

On the topic of the original post.... A structural comparison of protein fold type has proven very
useful in the construction of evolutionary groups of proteins - I am trying to start a project to do
the same for small molecules - Structural Classification of Ligands (SCOL) (re SCOP for proteins).

However - this is not easy - in the given example the similarity between haem and chlorophyl is both
structural and physiochemical - how should we begin to classify chemical structures into an overal
hierarchy?

I beleive such a framework would be a first step towards answering questions like 'which came first'
above. For example - how old is colesterol? - No doubt not as old as Fe4S, but how about glucose?

Anybody want to work on SCOL?

(hopefully) bioinformatics.orgbioinformatics.orgOpen ↗

I know there are many small molecule similarity (searching) algorithms out their - The first step is
to pick a few of these and see what comes out.

Cheers, Dan.

I had no idea hemoglobin was so old. Is there, by any chance, a similar paper on the history of the
chlorophyll gene? Bartosz

"r norman" <rsn_@_comcast.net> wrote in message "]news:[email hidden]...

Quoted message said:

Bartosz Milewski said:

Is the similarity between hemoglobin and chlorophyll an accident or did

one

Quoted message said:

Quoted message said:

evolve from the other?

You should read Ross C. Hardison A brief history of hemoglobins: Plant, animal, protist, and
bacteria Proc. Natl. Acad. Sci. USA, Vol. 93, pp. 5675-5679, June 1996

pnas.org5675.pdfOpen ↗

Quoted message said:

It starts out: "The utility of metal-bound porphyrin rings for the transfer of electrons was
established early in evolution, as witnessed by the ubiquitous cytochromes that pass electrons
down an electrochemical gradient in the respiratory chain,..."

It continues: "Plants not only make oxygen during photosynthesis, but they also use it for
respiration through the electron transfer chain in mitochondria. Recent studies show that they use
hemoglobins to bind and transfer that oxygen."

So it shouldn't be surprising that the oxygen-binding, energy translating porphyrin ring should be
common to both plant and animal.

Of course, the heme group is different from the globin protein. The paper's Figure 1 outlines the
history of the hemoglobin gene.

Sounds like you are still confusing the history of a gene or protein with
that of a molecule. A careful rereading of some of the other great
responses to your question should help to shed some light on this
misunderstanding. Chlorophyll is a molecule that requires something like 2
dozen proteins to synthesize (the first half or so of these are also used to
synthesize heme, hence the idea that heme is older than chlorophyll). There
are ideas that the history of these biosynthesis genes should mirror the
history of the molecule (e.g. Morowitz's "metabolism recapitulates
biogenesis"😉, and some nice but maybe too technical papers attempt to do
exactly this (e.g. Xiong et al. "Complex evolution of photosynthesis" in
Annual Review of Plant Biology 2002, 53:503-21).

"Bartosz Milewski" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

I had no idea hemoglobin was so old. Is there, by any chance, a similar paper on the history of
the chlorophyll gene? Bartosz

Bartosz Milewski said:

I had no idea hemoglobin was so old. Is there, by any chance, a similar paper on the history of the
chlorophyll gene? Bartosz

Try DH Burke, JE Hearst, and A Sidow Early Evolution of Photosynthesis: Clues from Nitrogenase \ and
Chlorophyll Iron Proteins PNAS 1993; 90: 7134-7138. pnas.org7134.pdfOpen ↗

or PETER J. LOCKHART*, ANTHONY W. D. LARKUM†, MICHAEL A. STEEL‡, PETER J. WADDELL*, AND DAVID PENNY*
Evolution of chlorophyll and bacteriochlorophyll: The problem of invariant sites in sequence
analysis Proc. Natl. Acad. Sci. USA 93, pp. 1930–1934, March 1996
pnas.org1930.pdfOpen ↗

"Bartosz Milewski" <[email hidden]> wrote in message

Quoted message said:

I had no idea hemoglobin was so old. Is there, by any chance, a similar paper on the history of
the chlorophyll gene?

Hemoglobin is protein, actually four units, plus four heme groups. An arrangement of four nitrogens
in the heme group holds the iron ion that gives hemoglobin its power to bind oxygen. Chlorophyll is
not a protein. It is a molecule that is similar to heme in that it has four nitrogens, in this case
holding a magnesium ion.

Since these molecules are not coded for directly by DNA, they can't undergo molecular evolution as
the term is generally understood. However the form of the molecules may have changed over
evolutionary time as the enzymes which synthesise these molecules changed.