Biology Reference
In-Depth Information
The relationship of
N. commune
GlbN, closer to the protozoan globins than
vertebrate globins or a bacterial globin such as that from
Vitreoscilla
(
Wakabayashi, Matsubara, & Webster, 1986
), was immediately intriguing.
The seminal contribution attracted attention to the presence of myoglobin-
like proteins in organisms that were not, up to then, known to use this
particular kind of haem protein.
Two years later, Guertin and co-workers published the observation of
light-induced (LI) globins in the unicellular green alga
Chlamydomonas
eugametos
(
Couture, Chamberland, St-Pierre, Lafontaine, & Guertin,
1994
). Like the
N. commune
and protozoan globins, the haem domains of
the
C. eugametos
Hbs were shorter than their vertebrate counterparts. For
this reason, these odd proteins were collectively called 'truncated' globins.
Several years later, the same group (
Couture et al., 2000
) and ours (
Scott &
Lecomte, 2000
) reported the preliminary characterization of the globin from
the cyanobacterium
Synechocystis
sp. PCC 6803. In contrast to
N. commune
glbN
, the position of
Synechocystis
sp. PCC 6803
glbN
within the genome
(
Kaneko et al., 1996
) held no functional hint. Soon thereafter, a
glbN
gene
was also found in the cyanobacterium
Synechococcus
sp. PCC 7002, and the
gene product was prepared by recombinant means (
Scott et al., 2002
).
Again, gene location did not suggest a functional role. The two strains of
Synechocystis
sp. and
Synechococcus
sp. added new members to the growing
truncated globin family, but little insight into the possible roles of the globins
in cyanobacteria.
Truncated globins are present not only in cyanobacteria and green
algae but also in many bacteria (
Vinogradov, Tinajero-Trejo, Poole, &
Hoogewijs, 2013
), fungi (
Hoogewijs, Dewilde, Vierstraete, Moens, &
Vinogradov, 2012
) and plants (
Vinogradov, Fernandez, et al., 2011
). As
early as 2002, it became possible to initiate a phylogenetic analysis of the
family. Thus,
Wittenberg, Bolognesi, Wittenberg, & Guertin, 2002
deter-
mined that truncated haemoglobins (TrHbs) could be separated into three
distinct groups, referred to as N (Group I), O (Group II) and P (Group
III). Later phylogenetic analyses (
Vinogradov et al., 2007; Vuletich &
Lecomte, 2006
) based on an increased number of sequences confirmed this
interpretation of the genomic record. To this date, all the truncated globins
of cyanobacteria belong to Group I. The majority of truncated globins in
green algae are also Group I proteins; however, a few Group II globins
are found in these organisms (Group II proteins dominate in diatoms and
higher plants,
Vinogradov, Fernandez, et al., 2011
).
