This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
4nen
From Proteopedia
An internal ligand-bound, metastable state of a leukocyte integrin, aXb2
Structural highlights
Disease[ITB2_HUMAN] Defects in ITGB2 are the cause of leukocyte adhesion deficiency type 1 (LAD1) [MIM:116920]. LAD1 patients have recurrent bacterial infections and their leukocytes are deficient in a wide range of adhesion-dependent functions.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] Function[ITAX_HUMAN] Integrin alpha-X/beta-2 is a receptor for fibrinogen. It recognizes the sequence G-P-R in fibrinogen. It mediates cell-cell interaction during inflammatory responses. It is especially important in monocyte adhesion and chemotaxis. [ITB2_HUMAN] Integrin alpha-L/beta-2 is a receptor for ICAM1, ICAM2, ICAM3 and ICAM4. Integrins alpha-M/beta-2 and alpha-X/beta-2 are receptors for the iC3b fragment of the third complement component and for fibrinogen. Integrin alpha-X/beta-2 recognizes the sequence G-P-R in fibrinogen alpha-chain. Integrin alpha-M/beta-2 recognizes P1 and P2 peptides of fibrinogen gamma chain. Integrin alpha-M/beta-2 is also a receptor for factor X. Integrin alpha-D/beta-2 is a receptor for ICAM3 and VCAM1. Triggers neutrophil transmigration during lung injury through PTK2B/PYK2-mediated activation.[12] Publication Abstract from PubMedHow is massive conformational change in integrins achieved on a rapid timescale? We report crystal structures of a metastable, putative transition state of integrin alphaXbeta2. The alphaXbeta2 ectodomain is bent; however, a lattice contact stabilizes its ligand-binding alphaI domain in a high affinity, open conformation. Much of the alphaI alpha7 helix unwinds, loses contact with the alphaI domain, and reshapes to form an internal ligand that binds to the interface between the beta propeller and betaI domains. Lift-off of the alphaI domain above this platform enables a range of extensional and rotational motions without precedent in allosteric machines. Movements of secondary structure elements in the beta2 betaI domain occur in an order different than in beta3 integrins, showing that integrin beta subunits can be specialized to assume different intermediate states between closed and open. Mutations demonstrate that the structure trapped here is metastable and can enable rapid equilibration between bent and extended-open integrin conformations and up-regulation of leukocyte adhesiveness. An internal ligand-bound, metastable state of a leukocyte integrin, alphaXbeta2.,Sen M, Yuki K, Springer TA J Cell Biol. 2013 Nov 25;203(4):629-42. doi: 10.1083/jcb.201308083. PMID:24385486[13] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
| ||||||||||||||||||||||
Categories: Human | Sen, M | Springer, T A | Yuki, K | Cell adhesion | Complement receptor | Denaturated protein | Fibrinogen | Heparin | Ic3b | Icam | Membrane | N-linked glycosylation
