Table 2.

Structural characteristics and tissue distributions of β subunits

Integrin subunits	Molecular weight (kDa)	Heterodimeric type	Structural characteristics	Tissue distributions	References
β1	115	α1β1, α2β1, α3β1, α4β1, α5β1, α6β1, α7β1, α8β1, α9β1, α10β1, α11β1, αvβ1	Has 56 residues in four repeat regions and internally disulphide bounded	Widely distributed	Isacke and Horton (2000)
β2	95	αDβ2, αLβ2, αMβ2, αXβ2	Cytoplasmic tail contains eight potential phosphorylation sites	Leucocytes	Isacke and Horton (2000), Takada et al. (2007)
β3	105	αvβ3, αIIbβ3	Its Tyr 773 is potentially phosphorylated	Platelets and macrophages	Coppolino and Dedhar (2000), Isacke and Horton (2000), Mor-Cohen (2016)
β4	220	α6β4	Contains a large cytoplasmic domain approximately 1000 amino acids	Epithelial cells	Mercurio et al. (2001)
β5	100	αvβ5		Neural crest cells, blood vessels and tumors	Memmo and McKeown-Longo (1998), Hu et al. (2014)
β6	105	αvβ6	Has a small cytoplasmic extension with unique 11 amino acids	Epithelial cells	Bandyopadhyay and Raghavan (2009)
β7	110	α4β7, αEβ7	Has two NPX(Y/F) motifs for potential tyrosine kinase binding	NK cells, B cells, eosinophils, intraepithelial cells, lymphocytes and peripheral cells	Schippers et al. (2012)
β8	95	αvβ8	No interact with cytoskeleton	Kidney, placenta, uterus, ovary and transformed cell lines	Isacke and Horton (2000)