Induction of the polymerization of actin from the actin:thymosin β4 complex by phalloidin, skeletal myosin subfragment 1, chicken intestinal myosin I and free ends of filamentous actin

Ballweber, Edda; Hannappel, Ewald; Niggemeyer, Brigitte; Mannherz, Hans Georg

doi:10.1111/j.1432-1033.1994.tb19009.x

Cited by 15 publications

(10 citation statements)

References 35 publications

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“…The β‐thymosins inhibit the salt induced polymerization of actin [2–4, 22]. When added to F‐actin, β‐thymosins were shown to induce its slow depolymerization [23].…”

Section: Resultsmentioning

confidence: 99%

Plant profilin induces actin polymerization from actin:β‐thymosin complexes and competes directly with β‐thymosins and with negative co‐operativity with DNase I for binding to actin

Ballweber

Giehl²,

Hannappel

et al. 1998

FEBS Letters

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Recombinant plant (birch) profilin was analyzed for its ability to promote actin polymerization from the actin:thymosin L L R and L L W complex. Depending on the nature of the divalent cation, recombinant plant (birch) profilin exhibited two different modes of interaction with actin, like mammalian profilin. In the presence of magnesium ions birch profilin promoted the polymerization of actin from A:TL L R . In contrast, in the presence of calcium but absence of magnesium ions birch profilin was unable to initiate the polymerization of actin from the complex with TL L R . However, under these conditions profilin formed a stable stoichiometric complex with skeletal muscle K Kactin, as verified by its ability to increase the critical concentration of actin polymerization. Chemical cross-linking indicated that birch profilin competes with TL L R for actin binding. Ternary complex formation of birch profilin with actin:DNase I complex was suggested by chemical cross-linking. However, the determination of the critical concentrations of actin polymerization in the simultaneous presence of birch profilin and DNase I indicated that profilin and DNase I did not form a ternary complex. These data indicated a negative co-operativity between the profilin and DNase I binding sites on actin.z 1998 Federation of European Biochemical Societies.

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“…The β‐thymosins inhibit the salt induced polymerization of actin [2–4, 22]. When added to F‐actin, β‐thymosins were shown to induce its slow depolymerization [23].…”

Section: Resultsmentioning

confidence: 99%

Plant profilin induces actin polymerization from actin:β‐thymosin complexes and competes directly with β‐thymosins and with negative co‐operativity with DNase I for binding to actin

Ballweber

Giehl²,

Hannappel

et al. 1998

FEBS Letters

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“…From the TiM-complexed monomers, polymerization can be started in vitro either by decapping barbed ends of filaments [5,6], or by adding nucleus stabilizers such as myosin S1 or phalloidin [7][8][9][10][11]. The relatively low affinity of T~4 for actin (ca.…”

Section: In~oductionmentioning

confidence: 99%

The ternary complex of DNase I, actin and thymosin β4

et al. 1996

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Key words: Actin; Thymosin 134; DNase I; Ternary complex; Thiol-specific crosslinking the differently positioned thiol groups in TIM come close enough to distinct thiol groups in actin to allow the formation of crosslinks. In this way two contact sites between the two proteins could be identified, one between the C-terminus of actin (Cys 374) and position 6 of TIM and a second between the )'-phosphate of the actin-bound nucleotide in actin and the sequence 17 28 in TIM.X-ray analysis of monomeric actin took advantage of a facilitated crystallization of actin when complexed with DNase I. Provided DNase I exerted a similar effect on TIMactin as well, co-crystallization with DNase I would allow the interface of actin and TIM in the ternary complex to be studied. Corresponding complexes have been reported for DNase I, actin and profilin, or ADF/cofilin, respectively [14,15]. However, the ternary complex can be expected to form only if the binding of DNase I and that of TIM to actin do not strongly interfere. We therefore examined whether DNase I affects the affinity of TIM for actin by studying one of the crosslinking reactions mentioned above in the presence of DNase I. Materials and methods In~oductionThymosin 134 (TIM) is one of the small proteins in nonmuscle cells that bind to monomeric actin and thus prevent unregulated polymerization [14]. From the TiM-complexed monomers, polymerization can be started in vitro either by decapping barbed ends of filaments [5,6], or by adding nucleus stabilizers such as myosin S1 or phalloidin [7][8][9][10][11]. The relatively low affinity of T~4 for actin (ca. 1 ~tM [4]) may be functionally significant in allowing the instant release of polymerizable actin into cytoplasm, if required.Since an X-ray analysis of the actin-TiM complex has so far not been achieved we have tried to identify contact sites between the two proteins by a chemical approach [12]. For this, five TIM analogs were synthesized, each of them with one cysteine residue substituted for a hydrophobic amino acid in the TIM chain. Using a set of thiol-specific crosslinkers of varying length, we assayed whether in the complex with actin

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“…These observations suggest that the control of polymerization does not depend on a change in affinity of Tfl4 for G-actin, but rather on the availability of free barbed-ends. Control of polymerization by this mechanism has recently been demonstrated in vitro [7].…”

Section: Introductionmentioning

confidence: 99%

Cap Z, a calcium insensitive capping protein in resting and activated platelets

et al. 1996

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Capping of the barbed-ends of actin filaments is an important mechanism for control of the cytoskeleton. In platelets, a valuable model system, it has been thought that gelsolin was the major capping protein. We now report that platelets contain ~2 btM Cap Z, a calcium insensitive heterodimeric capping protein; two major and additional minor isoforms of both a and ~ subunits are present. In lysates from resting platelets 75-80% of the Cap Z sediments with the high speed pellet, but if the platelets are activated with thrombin for 10 s, about 15% of the Cap Z leaves the pellet fraction and is found in the high speed supernatant where it is not bound to actin. This translocation of Cap Z to the supernatant is also observed when resting platelets are lysed into buffer containing 50-100 pM GTPTS and 10 mM EGTA. Our results suggest that release of Cap Z from some actin filaments could generate free filament barbed-ends. An increase in free barbed-ends has been reported in platelet lysates prepared shortly after thrombin activation.

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Induction of the polymerization of actin from the actin:thymosin β4 complex by phalloidin, skeletal myosin subfragment 1, chicken intestinal myosin I and free ends of filamentous actin

Cited by 15 publications

References 35 publications

Plant profilin induces actin polymerization from actin:β‐thymosin complexes and competes directly with β‐thymosins and with negative co‐operativity with DNase I for binding to actin

Plant profilin induces actin polymerization from actin:β‐thymosin complexes and competes directly with β‐thymosins and with negative co‐operativity with DNase I for binding to actin

The ternary complex of DNase I, actin and thymosin β4

Cap Z, a calcium insensitive capping protein in resting and activated platelets

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