The importance of C‐terminal amino acid residues of actin to the inhibition of actomyosin ATPase activity by caldesmon and troponin I

Makuch, Robert W.; Kolakowski, Janusz; Da̧browska, Renata

doi:10.1016/0014-5793(92)80546-s

Cited by 20 publications

(11 citation statements)

References 29 publications

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“…Interaction of calponin [8] and caldesmon [32][33][34] with Cterminal end of actin explains the previously observed competition between these two proteins for the binding to actin filaments [4]. The lower potency of caldesmon in displacing of calponin than the converse could be due to the bundling ability of calponin (at subsaturating ratio to F-actin) and thus its displacement only from non-cross-linked actin filaments.…”

Section: Discussionmentioning

confidence: 69%

Interaction of calponin with actin and its functional implications

Kolakowski

Makuch

Stȩpkowski

et al. 1995

Biochemical Journal

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Titration of F-actin with calponin causes the formation of two types of complexes. One, at saturation, contains a lower ratio of calponin to actin (0.5:1) and is insoluble at physiological ionic strength. The another is soluble, with a higher ratio of calponin to actin (1:1). Electron microscopy revealed that the former complex consists of paracrystalline bundles of actin filaments, whereas the latter consists of separate filaments. Ca(2+)-calmodulin causes dissociation of bundles with simultaneous increase in the number of separate calponin-containing filaments. Further increase in the calmodulin concentration results in full release of calponin from actin filaments. In motility assays, calponin, when added together with ATP to actin filaments complexed with immobilized myosin, evoked a decrease in both the number and velocity of moving actin filaments. Addition of calponin to actin filaments before their binding to myosin resulted in a formation of actin filament bundles which were dissociated by ATP.

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Section: Discussionmentioning

confidence: 69%

Interaction of calponin with actin and its functional implications

Kolakowski

Makuch

Stȩpkowski

et al. 1995

Biochemical Journal

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“…According to the atomic model of actin complexed with gelsolin segment 1, which plays a central role in the severing and capping activities of gelsolin, the cleft between subdomain 3 and subdomain 1 of actin serves as a docking region for gelsolin [31]. Therefore the association of caldesmon with the C-terminal region of actin [32,33], which is located near the cleft, may induce conformational changes in actin and affect its interaction with gelsolin.…”

Section: Discussionmentioning

confidence: 99%

Modulation of gelsolin-induced actin-filament severing by caldesmon and tropomyosin and the effect of these proteins on the actin activation of myosin Mg2+-ATPase activity

Da̧browska

Hinssen

Gała̧zkiewicz

et al. 1996

Biochemical Journal

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We have investigated the cumulative effects of three smoothmuscle actin-binding proteins, gelsolin, caldesmon and tropomyosin, on actin activation of myosin Mg# + -ATPase activity under low-ionic-strength conditions. A combination of tropomyosin (at a stoicheiometric ratio to actin) and gelsolin (at a molar ratio to actin of up to 1 : 100) showed essentially additive stimulatory effects that were counteracted by caldesmon. Suppression of the gelsolin-induced activation of the ATPase by caldesmon was higher in the presence of tropomyosin although it was not complete even at stoicheiometric amounts of both proteins to actin. Since activation of actin-activated ATPase activity of myosin by gelsolin is related to its severing action, it is concluded that caldesmon and tropomyosin cannot fully

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“…This reduced mobility, however, does not mean that in the polymer the C-terminus is buried in an intersubunit interface, since in F actin Cys374 [27], as well as the lysine residue next to it, [38] are easily accessible for modifying reagents. It has further been proposed that Cys374 may play a role in the interaction of actin with profilin [39], caldesmon and troponin C [40]. These observations set the scene for the question we wanted to answer: what is the function of the C-terminus in filament assembly?…”

Section: Discussionmentioning

confidence: 99%

Cooperative effects on filament stability in actin modified at the C‐terminus by substitution or truncation

Drewes

Faulstich

1993

European Journal of Biochemistry

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We have studied the contribution of the C-terminus of actin to filament stability by chemical modification and limited proteolysis. Formation of mixed disulfides of the penultimate C-terminal cysteine residue 374 with various low-molecular-mass thiols resulted in filament destabilization, as reflected by an increase in critical concentration and steady-state ATPase activity. These effects were fully reversed by the addition of phalloidin. Both the destabilization by glutathionylation and the reversal of it by phalloidin exhibited a high degree of cooperativity ; half-maximal destabilization required the modification of four out of five actin subunits, and half-maximal restabilization by phalloidin was already reached when only one out of 20 actin subunits was complexed. C-terminal truncation by limited trypsinolysis of filamentous actin resulted in a similar destabilization of the polymer, as shown by a 2-3-fold increase in the steady-state ATPase activity. This effect was likewise cooperative and could be reversed by phalloidin. Since truncation of the C-terminus of actin has an effect on stability similar to that of chemical modification with bulky substituents, the possibility can be excluded that, in the latter case, destabilization was caused by steric hindrance. Rather, it seems that the highly conserved C-terminal part of actin plays an active role in establishing a tight contact between neighbouring subunits.Under physiological conditions, actin exists as a long, apparently double-stranded helical array of globular monomers (reviewed in [l-31). Recently, atomic models of the filament were presented based on X-ray diffraction [4, 51and electron microscopy [6, 71. From these models, it was proposed that actin units in the filament exhibit strong longitudinal interactions but only tenuous diagonal interactions. It was shown that the C-terminus is probably localized at the bottom of the outer domain, not far from both contact sites [7]. The C-terminal residues of actin show a high degree of flexibility [8, 91. This may explain why, prior to crystallization of the DNAse complex, the three C-terminal residues, Lys373, Cys374 and Phe375, had to be removed by limited proteolysis [lo]. It may be that the C-terminal part of the molecule has a function in the assembly process. This is suggested by experiments with reporter groups attached to Cys374, which show that the environment of the C-terminus is changed during polymerization [8, 9, 11 -131.During our studies on the chemistry of the thiol groups of actin, we prepared some mixed disulfides of the protein with small thiol compounds [14-181. We observed that modification of Cys374, for example by formation of a mixed disulfide with glutathione, could greatly influence fila- Enzyme. Trypsin (EC 3.4.21.4). ment stability [15]. Based on the enhanced steady-state ATPase accompanying filament destabilization, the modification could be used to screen potentially filament-stabilizing agents and study their mechanism of action [16]. In a different approach, we succeeded ...

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The importance of C‐terminal amino acid residues of actin to the inhibition of actomyosin ATPase activity by caldesmon and troponin I

Cited by 20 publications

References 29 publications

Interaction of calponin with actin and its functional implications

Interaction of calponin with actin and its functional implications

Modulation of gelsolin-induced actin-filament severing by caldesmon and tropomyosin and the effect of these proteins on the actin activation of myosin Mg2+-ATPase activity

Cooperative effects on filament stability in actin modified at the C‐terminus by substitution or truncation

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