Altered conformation of Gc (Vitamin D-binding protein) upon complexing with cellular actin

Goldschmidt‐Clermont, Pascal J.; Williams, Merfyn H.; Galbraith, Robert M.

doi:10.1016/0006-291x(87)90572-9

Cited by 18 publications

(10 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The fact that both DBP and actin undergo only minor changes after complex formation indicates that DBP in the bloodstream is ''primed'' for actin binding. It has been proposed, however, that the rapid clearance of the actin-DBP complex from circulation is caused by a conformational change in DBP induced by actin binding (33). Our results do not support this view but instead would indicate that it is the complex itself that is recognized for clearance.…”

Section: Resultscontrasting

confidence: 99%

Crystal structures of the vitamin D-binding protein and its complex with actin: Structural basis of the actin-scavenger system

Otterbein

Cosio

Graceffa

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

150

121

View full text Add to dashboard Cite

Actin is the most abundant protein in eukaryotic cells, but its release from cells into blood vessels can be lethal, being associated with clinical situations including hepatic necrosis and septic shock. A homeostatic mechanism, termed the actin-scavenger system, is responsible for the depolymerization and removal of actin from the circulation. During the first phase of this mechanism, gelsolin severs the actin filaments. In the second phase, the vitamin Dbinding protein (DBP) traps the actin monomers, which accelerates their clearance. We have determined the crystal structures of DBP by itself and complexed with actin to 2.1 Å resolution. Similar to its homologue serum albumin, DBP consists of three related domains. Yet, in DBP a strikingly different organization of the domains gives rise to a large actin-binding cavity. After complex formation the three domains of DBP move slightly to ''clamp'' onto actin subdomain 3 and to a lesser extent subdomain 1. Contacts between actin and DBP throughout their extensive 3,454-Å 2 intermolecular interface involve a mixture of hydrophobic, electrostatic, and solventmediated interactions. The area of actin covered by DBP within the complex approximately equals the sum of those covered by gelsolin and profilin. Moreover, certain interactions of DBP with actin mirror those observed in the actin-gelsolin complex, which may explain how DBP can compete effectively with gelsolin for actin binding. Formation of the strong actin-DBP complex proceeds with limited conformational changes to both proteins, demonstrating how DBP has evolved to become an effective actin-scavenger protein.

show abstract

Section: Resultscontrasting

confidence: 99%

Crystal structures of the vitamin D-binding protein and its complex with actin: Structural basis of the actin-scavenger system

Otterbein

Cosio

Graceffa

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

150

121

View full text Add to dashboard Cite

show abstract

“…Fluorescence excitation was at 360 nm and emission was scanned from 360-560 nm (McClure and Edelman, 1966;Goldschmidt-Clermont et al, 1987). The signal obtained with TNS alone was compared with that obtained with TNS in the presence of PIP2 (10MM) and/or human platelet profilin (7 AM) and in separate assays, MgCI2 (10 mM) and/or PIP2 (10 M).…”

Section: Tns Fluorescencementioning

confidence: 99%

The affinities of human platelet and Acanthamoeba profilin isoforms for polyphosphoinositides account for their relative abilities to inhibit phospholipase C.

1990

View full text Add to dashboard Cite

In light of recent work implicating profilin from human platelets as a possible regulator of both cytoskeletal dynamics and inositol phospholipid-mediated signaling, we have further characterized the interaction of platelet profilin and the two isoforms of Acanthamoeba profilin with inositol phospholipids. Profilin from human platelets binds to phosphatidylinositol-4-monophosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2) with relatively high affinity (Kd approximately 1 microM for PIP2 by equilibrium gel filtration), but interacts only weakly (if at all) with phosphatidylinositol (PI) or inositol trisphosphate IP3) in small-zone gel-filtration assays. The two isoforms of Acanthamoeba profilin both have a lower affinity for PIP2 than does human platelet profilin, but the more basic profilin isoform from Acanthamoeba (profilin-II) has a much higher (approximately 10-microM Kd) affinity than the acidic isoform (profilin-I, 100 to 500-microM Kd). None of the profilins bind to phosphatidylserine (PS) or phosphatidylcholine (PC) in small-zone gel-filtration experiments. The differences in affinity for PIP2 parallel the ability of these three profilins to inhibit PIP2 hydrolysis by soluble phospholipase C (PLC). The results show that the interaction of profilins with PIP2 is specific with respect to both the lipid and the proteins. In Acanthamoeba, the two isoforms of profilin may have specialized functions on the basis of their identical (approximately 10 microM) affinities for actin monomers and different affinities for PIP2.

show abstract

“…1A). The binding of TNS to native DBP (or albumin) produces a strong increase in fluorescence emission at 465 nm (Goldschmidt-Clermont et al, 1987). Using purified alternative pathway proteins (C3, factor B, factor D) at physiological concentrations with 0.5 mM Mg 2+ , denatured DBP formed noticeably more complexes with C3b as compared to native DBP (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…To examine this possibility, C3b:DBP complexes were first formed in vitro using native DBP and then tested for the ability of DBP to bind actin while covalently coupled to C3b. DBP is a known actin monomer binding protein and it binds G-actin in 1:1 molar ratio with high affinity ( K d of 10 −9 M), and denaturation of DBP completely abolishes this function (Chun, 2012; Goldschmidt-Clermont et al, 1987). Purified C3b:DBP complexes were allowed to react with a 5-fold molar excess of purified G-actin and samples then were evaluated using an 8% non-denaturing gel to maintain the non-covalent DBP-actin complexes (Fig.…”

Section: Resultsmentioning

confidence: 99%

Enhanced recognition of plasma proteins in a non-native state by complement C3b. A possible clearance mechanism for damaged proteins in blood

Ramadass

Ghebrehiwet

Kew

2015

Molecular Immunology

View full text Add to dashboard Cite

Complement C3 is a key fluid-phase protein of the immune system that covalently tags pathogenic cells and molecules for subsequent clearance. Previously, we reported that complement activation results in the formation of multiple C3b:plasma protein complexes in serum. However, it is not known if C3b attaches to any plasma protein in close proximity or preferentially binds damaged proteins. The objective of this study was to determine if C3b couples to plasma proteins in a non-native state and if this could be a potential mechanism to detect and clear damaged proteins from the blood. Using a purified in vitro system with alternative pathway proteins C3, factors B and D it was observed that guanidinium-HCl denaturation of three purified plasma proteins (albumin, alpha-1 proteinase inhibitor, vitamin D binding protein) greatly increased their capacity to form covalent complexes with C3b. However, native vitamin D binding protein, covalently attached to C3b, still retained the ability to bind its natural ligand G-actin, indicating that C3b links to plasma proteins in their native configuration but denaturation substantially increases this interaction. Serum complement activation generated a large number of C3b:plasma protein complexes that bound red blood cell membranes, suggesting a CR1-mediated clearance mechanism. Thermally denatured (60°C) serum activated the alternative pathway when added to fresh serum as evidenced by factor B cleavage and iC3b generation, but this heat-treated serum could not generate the pro-inflammatory peptide C5a. These results show that C3 recognizes and tags damaged plasma proteins for subsequent removal from the blood without triggering proinflammatory functions.

show abstract

Altered conformation of Gc (Vitamin D-binding protein) upon complexing with cellular actin

Cited by 18 publications

References 27 publications

Crystal structures of the vitamin D-binding protein and its complex with actin: Structural basis of the actin-scavenger system

Crystal structures of the vitamin D-binding protein and its complex with actin: Structural basis of the actin-scavenger system

The affinities of human platelet and Acanthamoeba profilin isoforms for polyphosphoinositides account for their relative abilities to inhibit phospholipase C.

Enhanced recognition of plasma proteins in a non-native state by complement C3b. A possible clearance mechanism for damaged proteins in blood

Contact Info

Product

Resources

About