Editing Alpha-2-Macroglobulin (section)

== Structure ==
Human α<sub>2</sub>-macroglobulin is composed of four identical subunits bound together by [[SS-bond#Occurrence in proteins|-S-S- bonds]].<ref name="Andersen_1995">{{cite journal | vauthors = Andersen GR, Koch TJ, Dolmer K, Sottrup-Jensen L, Nyborg J | title = Low resolution X-ray structure of human methylamine-treated alpha 2-macroglobulin | journal = Journal of Biological Chemistry | volume = 270 | issue = 42 | pages = 25133–25141 | date = October 1995 | pmid = 7559647 | doi = 10.1074/jbc.270.42.25133 | s2cid = 86387917 | doi-access = free }}</ref><ref name="SottrupJensen_1984">{{cite journal | vauthors = Sottrup-Jensen L, Stepanik TM, Kristensen T, Wierzbicki DM, Jones CM, Lønblad PB | title = Primary structure of human alpha 2-macroglobulin. V. The complete structure. | journal = Journal of Biological Chemistry | volume = 259 | issue = 13 | pages = 8318–8327 | date = Jul 1984 | pmid = 6203908 | doi = 10.1016/S0021-9258(17)39730-2 | doi-access = free }}</ref> In addition to [[tetramer|tetrameric]] forms of α<sub>2</sub>-macroglobulin, [[dimer (chemistry)|dimeric]], and more recently [[monomer|monomeric]] αM protease inhibitors have been identified.<ref name="Dodds_1998">{{cite journal | vauthors = Dodds AW, Law SK | title = The phylogeny and evolution of the thioester bond-containing proteins C3, C4 and alpha 2-macroglobulin | journal = Immunological Reviews | volume = 166 | pages = 15–26 | date = December 1998 | pmid = 9914899 | doi = 10.1111/j.1600-065X.1998.tb01249.x | s2cid = 84262599 }}</ref><ref name="Armstrong_1999">{{cite journal | vauthors = Armstrong PB, Quigley JP | title = Alpha2-macroglobulin: an evolutionarily conserved arm of the innate immune system | journal = Developmental and Comparative Immunology | volume = 23 | issue = 4–5 | pages = 375–390 | year = 1999 | pmid = 10426429 | doi = 10.1016/s0145-305x(99)00018-x }}</ref>

Each monomer of human α<sub>2</sub>-macroglobulin is composed of several functional domains, including macroglobulin domains, a thiol ester-containing domain and a receptor-binding domain.<ref name="Doan_2007">{{cite journal | vauthors = Doan N, Gettins PG | title = Human alpha2-macroglobulin is composed of multiple domains, as predicted by homology with complement component C3. | journal = The Biochemical Journal | volume = 407 | issue = 1 | pages = 23–30 | date = Oct 2007 | pmid = 17608619 | pmc = 2267405 | doi = 10.1042/BJ20070764 }}</ref> Overall, α<sub>2</sub>-macroglobulin is the largest major nonimmunoglobulin protein in human plasma.

The [[amino acid sequence]] of α<sub>2</sub>-macroglobulin has been shown to be 71% the same as that of the [[pregnancy zone protein]] (PZP; also known as pregnancy-associated α<sub>2</sub>-glycoprotein).<ref>{{cite journal | vauthors = Devriendt K, Van den Berghe H, Cassiman JJ, Marynen P | title = Primary structure of pregnancy zone protein. Molecular cloning of a full-length PZP cDNA clone by the polymerase chain reaction | journal = Biochimica et Biophysica Acta | volume = 1088 | issue = 1 | pages = 95–103 | date = Jan 1991 | pmid = 1989698 | doi = 10.1016/0167-4781(91)90157-h }}</ref>