Editing Globin (section)

== Evolution ==
Globins [[evolution|evolved]] from a common ancestor and can be divided into three lineages:<ref name="pmid16061809">{{cite journal |last1=Vinogradov |first1=SN |last2=Hoogewijs |first2=D |last3=Bailly |first3=X |last4=Arredondo-Peter |first4=R |last5=Guertin |first5=M |last6=Gough |first6=J |last7=Dewilde |first7=S |last8=Moens |first8=L |last9=Vanfleteren |first9=JR |title=Three globin lineages belonging to two structural classes in genomes from the three kingdoms of life. |journal=Proceedings of the National Academy of Sciences of the United States of America |date=9 August 2005 |volume=102 |issue=32 |pages=11385–9 |doi=10.1073/pnas.0502103102 |pmid=16061809|pmc=1183549 |doi-access=free }}</ref><ref name=pmid23541529>{{cite journal |last1=Vinogradov |first1=Serge N. |last2=Tinajero-Trejo |first2=Mariana |last3=Poole |first3=Robert K. |last4=Hoogewijs |first4=David |title=Bacterial and archaeal globins — A revised perspective |journal=Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics |date=September 2013 |volume=1834 |issue=9 |pages=1789–1800 |doi=10.1016/j.bbapap.2013.03.021 |pmid=23541529|url=https://www.zora.uzh.ch/id/eprint/81249/1/Vingradov-Hoogewijs_BBA-Proteins_and_Proteomics_2013-main.pdf }}</ref>
* Family M (for myoglobin-like) or F (for FHb-like),<ref name="pmid32863222">{{cite journal |last1=Keppner |first1=A |last2=Maric |first2=D |last3=Correia |first3=M |last4=Koay |first4=TW |last5=Orlando |first5=IMC |last6=Vinogradov |first6=SN |last7=Hoogewijs |first7=D |title=Lessons from the post-genomic era: Globin diversity beyond oxygen binding and transport. |journal=Redox Biology |date=October 2020 |volume=37 |pages=101687 |doi=10.1016/j.redox.2020.101687 |pmid=32863222 |pmc=7475203}}</ref> which has a typical 3/3 fold.
** Subfamily FHb, for [[flavohaemoglobin]]s.  [[Fusion protein|Chimeric]].
** Subfamily SDgb, for single-domain globins (not to be confused with SSDgb).
* Family S (for sensor-like), again with a 3/3 fold.
** Subfamily GCS, for [[Globin-coupled sensor]]s. Chimeric.
** Subfamily PGb, for [[protoglobin]]s. Single-domain.
** Subfamily SSDgb, for sensor single-domain globins.
* Family T (for truncated), with a 2/2 fold<ref name="pmid26788940">{{cite journal |last1=Bustamante |first1=JP |last2=Radusky |first2=L |last3=Boechi |first3=L |last4=Estrin |first4=DA |last5=Ten Have |first5=A |last6=Martí |first6=MA |title=Evolutionary and Functional Relationships in the Truncated Hemoglobin Family. |journal=PLOS Computational Biology |date=January 2016 |volume=12 |issue=1 |pages=e1004701 |doi=10.1371/journal.pcbi.1004701 |pmid=26788940|pmc=4720485 |bibcode=2016PLSCB..12E4701B |doi-access=free }}</ref> All subfamilies can be chimeric, single-domain, or tandemly linked.<ref name="pmid32863222"/>
** Subfamily TrHb1 (also T1 or N).
** Subfamily TrHb2 (also T2 or O). Includes 2/2 [[phytoglobin]]s.
** Subfamily TrHb3 (also T3 or P).

The M/F family of globins is absent in [[archaea]]. Eukaryotes lack GCS, Pgb, and T3 subfamily globins.<ref name="pmid32863222"/>

Eight globins are known to occur in vertebrates: [[androglobin]] (Adgb), [[cytoglobin]] (Cygb), [[globin E]] (GbE, from bird eye), [[globin X]] (GbX, not found in mammals or birds), [[globin Y]] (GbY, from some mammals), [[hemoglobin]] (Hb), [[myoglobin]] (Mb) and [[neuroglobin]] (Ngb).<ref name="pmid32863222"/> All these types evolved from a single globin gene of F/M family<ref name="pmid32863222"/> found in basal animals.<ref>{{cite journal |last1=Burmester |first1=T |last2=Hankeln |first2=T |title=Function and evolution of vertebrate globins. |journal=Acta Physiologica |date=July 2014 |volume=211 |issue=3 |pages=501–14 |doi=10.1111/apha.12312 |pmid=24811692|s2cid=33770617 |doi-access=free }}</ref> The single gene has also invented an oxygen-carrying "hemoglobin" multiple times in other groups of animals.<ref>Solène Song, Viktor Starunov, Xavier Bailly, Christine Ruta, Pierre Kerner, Annemiek J.&nbsp;M. Cornelissen, Guillaume Balavoine: [https://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-020-01714-4 Globins in the marine annelid Platynereis dumerilii shed new light on hemoglobin evolution in bilaterians]. In: BMC Evolutionary Biology Vol.&nbsp;20, Issue&nbsp;165. 29 December 2020. [[doi:10.1186/s12862-020-01714-4]]. See also:
* [https://eurekalert.org/pub_releases/2020-12/c-asg122920.php A single gene 'invented' haemoglobin several times]. On: EurekAlert! 29 December 2020. Source: CNRS</ref> Several functionally different haemoglobins can coexist in the same [[species]].

=== Sequence conservation ===
Although the fold of the globin superfamily is highly [[evolution]]arily [[Conserved sequence|conserved]], the sequences that form the fold can have as low as 16% sequence identity. While the sequence specificity of the fold is not stringent, the [[hydrophobic core]] of the protein must be maintained and hydrophobic patches on the generally [[hydrophilic]] solvent-exposed surface must be avoided in order for the structure to remain stable and [[soluble]]. The most famous mutation in the globin fold is a change from [[glutamate]] to [[valine]] in one chain of the hemoglobin molecule. This mutation creates a "hydrophobic patch" on the protein surface that promotes intermolecular aggregation, the molecular event that gives rise to [[Sickle cell disease|sickle-cell disease]].{{Cn|date=November 2024}}