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From Proteopedia
Crystal structure of WT murine S100A9 bound to calcium and zinc
Structural highlights
FunctionS10A9_MOUSE S100A9 is a calcium- and zinc-binding protein which plays a prominent role in the regulation of inflammatory processes and immune response (PubMed:15331440, PubMed:17767165, PubMed:18403730, PubMed:19402754, PubMed:22804476, PubMed:34562450). It can induce neutrophil chemotaxis, adhesion, can increase the bactericidal activity of neutrophils by promoting phagocytosis via activation of SYK, PI3K/AKT, and ERK1/2 and can induce degranulation of neutrophils by a MAPK-dependent mechanism (By similarity). Predominantly found as calprotectin (S100A8/A9) which has a wide plethora of intra- and extracellular functions (By similarity). The intracellular functions include: facilitating leukocyte arachidonic acid trafficking and metabolism, modulation of the tubulin-dependent cytoskeleton during migration of phagocytes and activation of the neutrophilic NADPH-oxidase (PubMed:15331440). Activates NADPH-oxidase by facilitating the enzyme complex assembly at the cell membrane, transferring arachidonic acid, an essential cofactor, to the enzyme complex and S100A8 contributes to the enzyme assembly by directly binding to NCF2/P67PHOX (By similarity). The extracellular functions involve pro-inflammatory, antimicrobial, oxidant-scavenging and apoptosis-inducing activities (PubMed:21382888). Its pro-inflammatory activity includes recruitment of leukocytes, promotion of cytokine and chemokine production, and regulation of leukocyte adhesion and migration (By similarity). Acts as an alarmin or a danger associated molecular pattern (DAMP) molecule and stimulates innate immune cells via binding to pattern recognition receptors such as Toll-like receptor 4 (TLR4) and receptor for advanced glycation endproducts (AGER) (PubMed:17767165, PubMed:18403730, PubMed:19402754). Binding to TLR4 and AGER activates the MAP-kinase and NF-kappa-B signaling pathways resulting in the amplification of the pro-inflammatory cascade (PubMed:17767165, PubMed:18403730, PubMed:19402754, PubMed:22804476). Has antimicrobial activity towards bacteria and fungi and exerts its antimicrobial activity probably via chelation of Zn(2+) which is essential for microbial growth (By similarity). Can induce cell death via autophagy and apoptosis and this occurs through the cross-talk of mitochondria and lysosomes via reactive oxygen species (ROS) and the process involves BNIP3 (By similarity). Can regulate neutrophil number and apoptosis by an anti-apoptotic effect; regulates cell survival via ITGAM/ITGB and TLR4 and a signaling mechanism involving MEK-ERK (By similarity). Its role as an oxidant scavenger has a protective role in preventing exaggerated tissue damage by scavenging oxidants (By similarity). The iNOS-S100A8/A9 transnitrosylase complex is proposed to direct selective inflammatory stimulus-dependent S-nitrosylation of multiple targets such as GAPDH, NXA5, EZR, MSN and VIM by recognizing a [IL]-x-C-x-x-[DE] motif (By similarity).[UniProtKB:P06702][1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedS100A9, with its congener S100A8, belongs to the S100 family of calcium-binding proteins found exclusively in vertebrates. These two proteins are major constituents of neutrophils. In response to a pathological condition, they can be released extracellularly and become alarmins that induce both pro- and anti-inflammatory signals, through specific cell surface receptors. They also act as antimicrobial agents, mainly as a S100A8/A9 heterocomplex, through metal sequestration. The mechanisms whereby divalent cations modulate the extracellular functions of S100A8 and S100A9 are still unclear. Importantly, it has been proposed that these ions may affect both the ternary and quaternary structure of these proteins, thereby influencing their physiological properties. In the present study, we report the crystal structures of WT and C80A murine S100A9 (mS100A9), determined at 1.45 and 2.35 A resolution, respectively, in the presence of calcium and zinc. These structures reveal a canonical homodimeric form for the protein. They also unravel an intramolecular disulfide bridge that stabilizes the C-terminal tail in a rigid conformation, thus shaping a second Zn-binding site per S100A9 protomer. In solution, mS100A9 apparently binds only two zinc ions per homodimer, with an affinity in the micromolar range, and aggregates in the presence of excess zinc. Using mass spectrometry, we demonstrate that mS100A9 can form both non-covalent and covalent homodimers with distinct disulfide bond patterns. Interestingly, calcium and zinc seem to affect differentially the relative proportion of these forms. We discuss how the metal-dependent interconversion between mS100A9 homodimers may explain the versatility of physiological functions attributed to the protein. Divalent cations influence the dimerization mode of murine S100A9 protein by modulating its disulfide bond pattern.,Signor L, Paris T, Mas C, Picard A, Lutfalla G, Boeri Erba E, Yatime L J Struct Biol. 2021 Mar;213(1):107689. doi: 10.1016/j.jsb.2020.107689. Epub 2020 , Dec 31. PMID:33359632[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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