Biology Reference
In-Depth Information
SDgb
single-domain 3/3 globin related to the N-terminal of FHbs
SSDgb
sensor single-domain 3/3 globin related to the N-terminal of GCSs
1. OVERVIEW
Haemoglobins (Hbs) and related haemeproteins (e.g. myoglobin
(Mb)), that we call globins for short, undoubtedly represent the most studied
family of proteins. Furthermore, the determinations of the crystal and pri-
mary structures of horse heart haemoglobin and of sperm whale myoglobin
and of the sequences of their polypeptide chains in the 1950s mark the
beginning of protein molecular biology. Although it had become clear by
the mid-1990s that globins occurred in a wide variety of metazoans, in
microbial eukaryotes such as ciliates (
Iwaasa, Takagi, & Shikama, 1989;
Yamauchi, Tada, &Usuki, 1995
) and fungi (
Zhu &Riggs, 1992
), in bacteria
and were ubiquitous in plants (
Hardison, 1996; Hunt et al., 2001
), a detailed
panorama of the globin phylogenomic distribution was not revealed until
the arrival of bacterial genomic information. A bioinformatic survey of
the then available (
420) bacterial genomes (
Vinogradov et al., 2005
) dem-
onstrated the existence of three globin families, of which the
flavohaemoglobin (FHb) and globin-coupled sensor (GCS) families have
the canonical 3/3 Mb-fold, had been discovered by one of us (R. K. P.)
(
Vasudevan et al., 1991
) and by Alam and his collaborators (
Hou et al.,
2001
), respectively. The third family comprised globins with a novel, trun-
cated 2/2 Mb-fold, characterized by an absent or vestigial helix A and a loop
instead of helix E (
Pesce et al., 2000
). Although globins belonging to each of
the three families had already been recognized, additional bacterial genomes
demonstrated the presence of single-domain globins in the FHb and GCS
families (
Vinogradov et al., 2006, 2007
), indicating eight globin subfamilies
(
Vinogradov, Hoogewijs, Vanfleteren, et al., 2011
): FHbs and related
single-domain globins (SDgbs), the GCSs and two related, but distinct
single-domain sensor globins, protoglobins (Pgbs), discovered by Alam and
his collaborators (
Freitas, Saito, Hou, &Alam, 2005
) and sensor single-domain
globins (SSDgbs), and three classes of TrHbs, classes 1, 2 and 3 (
Vuletich &
Lecomte, 2006; Wittenberg, Bolognesi, Wittenberg, & Guertin, 2002
).
A recent update of the bacterial globin census based on over 2200 bacterial
and about 140 archaeal genomes has fully confirmed and extended earlier
findings (
Vinogradov, Tinajero-Trejo, Poole, & Hoogewijs, 2013
).
