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Aczonin, a 550-kD putative scaffolding protein of presynaptic active zones, shares homology regions with Rim and Bassoon and binds profilin.

Wang X, Kibschull M, Laue MM, Lichte B, Petrasch-Parwez E, Kilimann MW - J. Cell Biol. (1999)

Bottom Line: We report the identification and initial characterization of aczonin, a neuron-specific 550-kD protein concentrated at the presynaptic active zone and associated with a detergent-resistant cytoskeletal subcellular fraction.Aczonin binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics.Large parts of aczonin, including the zinc finger, PDZ, and C2 domains, are homologous to Rim or to Bassoon, two other proteins concentrated in presynaptic active zones.

View Article: PubMed Central - PubMed

Affiliation: Institut für Physiologische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.

ABSTRACT
Neurotransmitter exocytosis is restricted to the active zone, a specialized area of the presynaptic plasma membrane. We report the identification and initial characterization of aczonin, a neuron-specific 550-kD protein concentrated at the presynaptic active zone and associated with a detergent-resistant cytoskeletal subcellular fraction. Analysis of the amino acid sequences of chicken and mouse aczonin indicates an organization into multiple domains, including two pairs of Cys(4) zinc fingers, a polyproline tract, and a PDZ domain and two C2 domains near the COOH terminus. The second C2 domain is subject to differential splicing. Aczonin binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics. Large parts of aczonin, including the zinc finger, PDZ, and C2 domains, are homologous to Rim or to Bassoon, two other proteins concentrated in presynaptic active zones. We propose that aczonin is a scaffolding protein involved in the organization of the molecular architecture of synaptic active zones and in the orchestration of neurotransmitter vesicle trafficking.

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Aczonin binds profilin. Recombinant profilins I and II covalently coupled to Sepharose precipitate aczonin from mouse brain lysate (S, supernatant; P, pellet). Profilin binding is blocked by preincubation of the profilin resin with polyproline (PP), but not by polyalanine (PA). Immobilized BSA as a negative control does not precipitate aczonin. See Results for additional control experiments not shown.
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Figure 7: Aczonin binds profilin. Recombinant profilins I and II covalently coupled to Sepharose precipitate aczonin from mouse brain lysate (S, supernatant; P, pellet). Profilin binding is blocked by preincubation of the profilin resin with polyproline (PP), but not by polyalanine (PA). Immobilized BSA as a negative control does not precipitate aczonin. See Results for additional control experiments not shown.

Mentions: Profilin exists in two isoforms, profilin I being expressed in many tissues including brain, and profilin II predominating in brain and skeletal muscle (Witke et al. 1998). We expressed both isoforms as His-tag fusion proteins, coupled them to Sepharose resin, and could specifically precipitate aczonin from brain lysates with both (Fig. 7). Aczonin precipitation is blocked by preincubation of the profilin resins with synthetic polyproline but not by polyalanine, indicating that polyproline and aczonin compete for the same binding site on profilin, aczonin probably through its polyproline tract (Fig. 7).


Aczonin, a 550-kD putative scaffolding protein of presynaptic active zones, shares homology regions with Rim and Bassoon and binds profilin.

Wang X, Kibschull M, Laue MM, Lichte B, Petrasch-Parwez E, Kilimann MW - J. Cell Biol. (1999)

Aczonin binds profilin. Recombinant profilins I and II covalently coupled to Sepharose precipitate aczonin from mouse brain lysate (S, supernatant; P, pellet). Profilin binding is blocked by preincubation of the profilin resin with polyproline (PP), but not by polyalanine (PA). Immobilized BSA as a negative control does not precipitate aczonin. See Results for additional control experiments not shown.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2164979&req=5

Figure 7: Aczonin binds profilin. Recombinant profilins I and II covalently coupled to Sepharose precipitate aczonin from mouse brain lysate (S, supernatant; P, pellet). Profilin binding is blocked by preincubation of the profilin resin with polyproline (PP), but not by polyalanine (PA). Immobilized BSA as a negative control does not precipitate aczonin. See Results for additional control experiments not shown.
Mentions: Profilin exists in two isoforms, profilin I being expressed in many tissues including brain, and profilin II predominating in brain and skeletal muscle (Witke et al. 1998). We expressed both isoforms as His-tag fusion proteins, coupled them to Sepharose resin, and could specifically precipitate aczonin from brain lysates with both (Fig. 7). Aczonin precipitation is blocked by preincubation of the profilin resins with synthetic polyproline but not by polyalanine, indicating that polyproline and aczonin compete for the same binding site on profilin, aczonin probably through its polyproline tract (Fig. 7).

Bottom Line: We report the identification and initial characterization of aczonin, a neuron-specific 550-kD protein concentrated at the presynaptic active zone and associated with a detergent-resistant cytoskeletal subcellular fraction.Aczonin binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics.Large parts of aczonin, including the zinc finger, PDZ, and C2 domains, are homologous to Rim or to Bassoon, two other proteins concentrated in presynaptic active zones.

View Article: PubMed Central - PubMed

Affiliation: Institut für Physiologische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.

ABSTRACT
Neurotransmitter exocytosis is restricted to the active zone, a specialized area of the presynaptic plasma membrane. We report the identification and initial characterization of aczonin, a neuron-specific 550-kD protein concentrated at the presynaptic active zone and associated with a detergent-resistant cytoskeletal subcellular fraction. Analysis of the amino acid sequences of chicken and mouse aczonin indicates an organization into multiple domains, including two pairs of Cys(4) zinc fingers, a polyproline tract, and a PDZ domain and two C2 domains near the COOH terminus. The second C2 domain is subject to differential splicing. Aczonin binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics. Large parts of aczonin, including the zinc finger, PDZ, and C2 domains, are homologous to Rim or to Bassoon, two other proteins concentrated in presynaptic active zones. We propose that aczonin is a scaffolding protein involved in the organization of the molecular architecture of synaptic active zones and in the orchestration of neurotransmitter vesicle trafficking.

Show MeSH
Related in: MedlinePlus