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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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Regional organization of aczonin and partial homology to Bassoon and Rim. For aczonin, wide bars indicate sequence regions with high similarity between chicken and mouse, and narrow bars indicate sequences with low interspecies conservation. Triangles mark regions with 10-mer repeats, and ovoids mark the region with 22-mer repeats in the chicken sequence (actual repeat units are shorter and more numerous than these symbols). Black boxes represent zinc finger (Zn), polyproline (PP), PDZ, and C2 modules as indicated. Shaded boxes in Bassoon and Rim indicate additional sequence regions with similarity to aczonin. Cross-hatched boxes indicate a sequence region of particularly high conservation between mouse aczonin, chicken aczonin, and Bassoon. Regions of sequence similarity are connected by dashed lines. In aczonin, a vertical dashed line near the NH2 terminus indicates the end of the chicken sequence, and two vertical lines between the C2 modules indicate the sites of differential splicing.
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Figure 2: Regional organization of aczonin and partial homology to Bassoon and Rim. For aczonin, wide bars indicate sequence regions with high similarity between chicken and mouse, and narrow bars indicate sequences with low interspecies conservation. Triangles mark regions with 10-mer repeats, and ovoids mark the region with 22-mer repeats in the chicken sequence (actual repeat units are shorter and more numerous than these symbols). Black boxes represent zinc finger (Zn), polyproline (PP), PDZ, and C2 modules as indicated. Shaded boxes in Bassoon and Rim indicate additional sequence regions with similarity to aczonin. Cross-hatched boxes indicate a sequence region of particularly high conservation between mouse aczonin, chicken aczonin, and Bassoon. Regions of sequence similarity are connected by dashed lines. In aczonin, a vertical dashed line near the NH2 terminus indicates the end of the chicken sequence, and two vertical lines between the C2 modules indicate the sites of differential splicing.

Mentions: Aczonin was identified as a new molecular constituent of neuronal synapses by immunoscreening a brain cDNA expression library with antisera raised against synaptic plasma membranes (Lichte et al. 1992). An alignment of the cDNA-deduced mouse and chicken aczonin sequences with Bassoon is presented in Fig. 1, and an overview of the regional organization of the aczonin sequence and its similarities with Bassoon and Rim is given in Fig. 2. The longest splicing variant of mouse aczonin is predicted to be a 550-kD hydrophilic polypeptide of balanced charge (pI 6.4) featuring two mutually homologous pairs of Cys4 zinc fingers in the NH2-terminal region, a polyproline stretch in the middle (22 uninterrupted proline residues in the mouse and 11 in chicken), and a PDZ domain and two C2 motifs in the COOH-terminal region.


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)

Regional organization of aczonin and partial homology to Bassoon and Rim. For aczonin, wide bars indicate sequence regions with high similarity between chicken and mouse, and narrow bars indicate sequences with low interspecies conservation. Triangles mark regions with 10-mer repeats, and ovoids mark the region with 22-mer repeats in the chicken sequence (actual repeat units are shorter and more numerous than these symbols). Black boxes represent zinc finger (Zn), polyproline (PP), PDZ, and C2 modules as indicated. Shaded boxes in Bassoon and Rim indicate additional sequence regions with similarity to aczonin. Cross-hatched boxes indicate a sequence region of particularly high conservation between mouse aczonin, chicken aczonin, and Bassoon. Regions of sequence similarity are connected by dashed lines. In aczonin, a vertical dashed line near the NH2 terminus indicates the end of the chicken sequence, and two vertical lines between the C2 modules indicate the sites of differential splicing.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Regional organization of aczonin and partial homology to Bassoon and Rim. For aczonin, wide bars indicate sequence regions with high similarity between chicken and mouse, and narrow bars indicate sequences with low interspecies conservation. Triangles mark regions with 10-mer repeats, and ovoids mark the region with 22-mer repeats in the chicken sequence (actual repeat units are shorter and more numerous than these symbols). Black boxes represent zinc finger (Zn), polyproline (PP), PDZ, and C2 modules as indicated. Shaded boxes in Bassoon and Rim indicate additional sequence regions with similarity to aczonin. Cross-hatched boxes indicate a sequence region of particularly high conservation between mouse aczonin, chicken aczonin, and Bassoon. Regions of sequence similarity are connected by dashed lines. In aczonin, a vertical dashed line near the NH2 terminus indicates the end of the chicken sequence, and two vertical lines between the C2 modules indicate the sites of differential splicing.
Mentions: Aczonin was identified as a new molecular constituent of neuronal synapses by immunoscreening a brain cDNA expression library with antisera raised against synaptic plasma membranes (Lichte et al. 1992). An alignment of the cDNA-deduced mouse and chicken aczonin sequences with Bassoon is presented in Fig. 1, and an overview of the regional organization of the aczonin sequence and its similarities with Bassoon and Rim is given in Fig. 2. The longest splicing variant of mouse aczonin is predicted to be a 550-kD hydrophilic polypeptide of balanced charge (pI 6.4) featuring two mutually homologous pairs of Cys4 zinc fingers in the NH2-terminal region, a polyproline stretch in the middle (22 uninterrupted proline residues in the mouse and 11 in chicken), and a PDZ domain and two C2 motifs in the COOH-terminal region.

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