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Microtubule actin cross-linking factor (MACF): a hybrid of dystonin and dystrophin that can interact with the actin and microtubule cytoskeletons.

Leung CL, Sun D, Zheng M, Knowles DR, Liem RK - J. Cell Biol. (1999)

Bottom Line: However, unlike dystonin, mACF7 does not contain a coiled-coil rod domain; instead, the rod domain of mACF7 is made up of 23 dystrophin-like spectrin repeats.More importantly, we found that the COOH-terminal domain of mACF7 interacts with and stabilizes microtubules.The properties of MACF are consistent with the observation that mutations in kakapo cause disorganization of microtubules in epidermal muscle attachment cells and some sensory neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Department of Anatomy and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.

ABSTRACT
We cloned and characterized a full-length cDNA of mouse actin cross-linking family 7 (mACF7) by sequential rapid amplification of cDNA ends-PCR. The completed mACF7 cDNA is 17 kb and codes for a 608-kD protein. The closest relative of mACF7 is the Drosophila protein Kakapo, which shares similar architecture with mACF7. mACF7 contains a putative actin-binding domain and a plakin-like domain that are highly homologous to dystonin (BPAG1-n) at its NH(2) terminus. However, unlike dystonin, mACF7 does not contain a coiled-coil rod domain; instead, the rod domain of mACF7 is made up of 23 dystrophin-like spectrin repeats. At its COOH terminus, mACF7 contains two putative EF-hand calcium-binding motifs and a segment homologous to the growth arrest-specific protein, Gas2. In this paper, we demonstrate that the NH(2)-terminal actin-binding domain of mACF7 is functional both in vivo and in vitro. More importantly, we found that the COOH-terminal domain of mACF7 interacts with and stabilizes microtubules. In transfected cells full-length mACF7 can associate not only with actin but also with microtubules. Hence, we suggest a modified name: MACF (microtubule actin cross-linking factor). The properties of MACF are consistent with the observation that mutations in kakapo cause disorganization of microtubules in epidermal muscle attachment cells and some sensory neurons.

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Sequence analysis of mACF7 COOH-terminal domain. (A) The two putative EF-hand calcium binding motifs of mACF7 are compared with those of mouse calmodulin (CaM). The amino acids that contain side chains with oxygen atoms for Ca2+ binding are shaded in gray, whereas the highly conserved glycine and hydrophobic amino acid are shaded in black with white letters. (B) Sequence comparison of mACF7 GAR region, human KIAA 0465, Drosophila Kakapo, human GAR22, and human GAS2 protein. The identical amino acids are shaded. (C) Schematic representation of the domain structure of mACF7. The NH2-terminal head domain consists of an ABD and a plakin-like globular domain. The rod domain is composed of 23 dystrophin-like spectrin repeats. The COOH-terminal tail domain is composed of two EF-hand motifs (Ca2+) and a Gas2/GAR22 homology region (GAR). The number of the amino acids that marked the boundary of each domain is also indicated.
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Figure 2: Sequence analysis of mACF7 COOH-terminal domain. (A) The two putative EF-hand calcium binding motifs of mACF7 are compared with those of mouse calmodulin (CaM). The amino acids that contain side chains with oxygen atoms for Ca2+ binding are shaded in gray, whereas the highly conserved glycine and hydrophobic amino acid are shaded in black with white letters. (B) Sequence comparison of mACF7 GAR region, human KIAA 0465, Drosophila Kakapo, human GAR22, and human GAS2 protein. The identical amino acids are shaded. (C) Schematic representation of the domain structure of mACF7. The NH2-terminal head domain consists of an ABD and a plakin-like globular domain. The rod domain is composed of 23 dystrophin-like spectrin repeats. The COOH-terminal tail domain is composed of two EF-hand motifs (Ca2+) and a Gas2/GAR22 homology region (GAR). The number of the amino acids that marked the boundary of each domain is also indicated.

Mentions: The deduced amino acid sequence of mACF7 was used to search for homologous proteins in the GenBank database. The closest relative of mACF7 is the Drosophila protein Kakapo. mACF7 and Kakapo not only share homology in primary sequence but also the overall protein architecture, indicating that mACF7 is the mouse homologue of Kakapo. As described in the previous study (Bernier et al. 1996), mACF7 contains a dystonin/BPAG1-n homologous NH2-terminal region, which includes a calponin homology ABD and a globular plakin-like domain. Interestingly, following the NH2-terminal domains, the sequences of mACF7 and dystonin start to diverge. Sequence comparison of mACF7 with dystrophin revealed that the central region of mACF7 would fold into 23 spectrin repeats (Fig. 1 B). By analogy to β-spectrin, this collection of spectrin repeats would also constitute the rod domain (not a coiled–coil rod) of mACF7. Following the rod domain, two calmodulin-like, EF-hand calcium-binding motifs were identified (Fig. 2 A). Together, these features suggest that mACF7 is a new member of the spectrin superfamily with plakin-like features.


Microtubule actin cross-linking factor (MACF): a hybrid of dystonin and dystrophin that can interact with the actin and microtubule cytoskeletons.

Leung CL, Sun D, Zheng M, Knowles DR, Liem RK - J. Cell Biol. (1999)

Sequence analysis of mACF7 COOH-terminal domain. (A) The two putative EF-hand calcium binding motifs of mACF7 are compared with those of mouse calmodulin (CaM). The amino acids that contain side chains with oxygen atoms for Ca2+ binding are shaded in gray, whereas the highly conserved glycine and hydrophobic amino acid are shaded in black with white letters. (B) Sequence comparison of mACF7 GAR region, human KIAA 0465, Drosophila Kakapo, human GAR22, and human GAS2 protein. The identical amino acids are shaded. (C) Schematic representation of the domain structure of mACF7. The NH2-terminal head domain consists of an ABD and a plakin-like globular domain. The rod domain is composed of 23 dystrophin-like spectrin repeats. The COOH-terminal tail domain is composed of two EF-hand motifs (Ca2+) and a Gas2/GAR22 homology region (GAR). The number of the amino acids that marked the boundary of each domain is also indicated.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2168091&req=5

Figure 2: Sequence analysis of mACF7 COOH-terminal domain. (A) The two putative EF-hand calcium binding motifs of mACF7 are compared with those of mouse calmodulin (CaM). The amino acids that contain side chains with oxygen atoms for Ca2+ binding are shaded in gray, whereas the highly conserved glycine and hydrophobic amino acid are shaded in black with white letters. (B) Sequence comparison of mACF7 GAR region, human KIAA 0465, Drosophila Kakapo, human GAR22, and human GAS2 protein. The identical amino acids are shaded. (C) Schematic representation of the domain structure of mACF7. The NH2-terminal head domain consists of an ABD and a plakin-like globular domain. The rod domain is composed of 23 dystrophin-like spectrin repeats. The COOH-terminal tail domain is composed of two EF-hand motifs (Ca2+) and a Gas2/GAR22 homology region (GAR). The number of the amino acids that marked the boundary of each domain is also indicated.
Mentions: The deduced amino acid sequence of mACF7 was used to search for homologous proteins in the GenBank database. The closest relative of mACF7 is the Drosophila protein Kakapo. mACF7 and Kakapo not only share homology in primary sequence but also the overall protein architecture, indicating that mACF7 is the mouse homologue of Kakapo. As described in the previous study (Bernier et al. 1996), mACF7 contains a dystonin/BPAG1-n homologous NH2-terminal region, which includes a calponin homology ABD and a globular plakin-like domain. Interestingly, following the NH2-terminal domains, the sequences of mACF7 and dystonin start to diverge. Sequence comparison of mACF7 with dystrophin revealed that the central region of mACF7 would fold into 23 spectrin repeats (Fig. 1 B). By analogy to β-spectrin, this collection of spectrin repeats would also constitute the rod domain (not a coiled–coil rod) of mACF7. Following the rod domain, two calmodulin-like, EF-hand calcium-binding motifs were identified (Fig. 2 A). Together, these features suggest that mACF7 is a new member of the spectrin superfamily with plakin-like features.

Bottom Line: However, unlike dystonin, mACF7 does not contain a coiled-coil rod domain; instead, the rod domain of mACF7 is made up of 23 dystrophin-like spectrin repeats.More importantly, we found that the COOH-terminal domain of mACF7 interacts with and stabilizes microtubules.The properties of MACF are consistent with the observation that mutations in kakapo cause disorganization of microtubules in epidermal muscle attachment cells and some sensory neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Department of Anatomy and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.

ABSTRACT
We cloned and characterized a full-length cDNA of mouse actin cross-linking family 7 (mACF7) by sequential rapid amplification of cDNA ends-PCR. The completed mACF7 cDNA is 17 kb and codes for a 608-kD protein. The closest relative of mACF7 is the Drosophila protein Kakapo, which shares similar architecture with mACF7. mACF7 contains a putative actin-binding domain and a plakin-like domain that are highly homologous to dystonin (BPAG1-n) at its NH(2) terminus. However, unlike dystonin, mACF7 does not contain a coiled-coil rod domain; instead, the rod domain of mACF7 is made up of 23 dystrophin-like spectrin repeats. At its COOH terminus, mACF7 contains two putative EF-hand calcium-binding motifs and a segment homologous to the growth arrest-specific protein, Gas2. In this paper, we demonstrate that the NH(2)-terminal actin-binding domain of mACF7 is functional both in vivo and in vitro. More importantly, we found that the COOH-terminal domain of mACF7 interacts with and stabilizes microtubules. In transfected cells full-length mACF7 can associate not only with actin but also with microtubules. Hence, we suggest a modified name: MACF (microtubule actin cross-linking factor). The properties of MACF are consistent with the observation that mutations in kakapo cause disorganization of microtubules in epidermal muscle attachment cells and some sensory neurons.

Show MeSH
Related in: MedlinePlus