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Expression and genomic analysis of midasin, a novel and highly conserved AAA protein distantly related to dynein.

Garbarino JE, Gibbons IR - BMC Genomics (2002)

Bottom Line: Expression of hemagglutamin-tagged midasin in yeast demonstrates a polypeptide of the anticipated size that is localized principally in the nucleus.The highly conserved structure of midasin in eukaryotes, taken in conjunction with its nuclear localization in yeast, suggests that midasin may function as a nuclear chaperone and be involved in the assembly/disassembly of macromolecular complexes in the nucleus.The AAA domain of midasin is evolutionarily related to that of dynein, but it appears to lack a microtubule-binding site.

View Article: PubMed Central - HTML - PubMed

Affiliation: Molecular and Cell Biology Department, University of California Berkeley, 94720-3200, USA. joangarb@uclink4.berkeley.edu

ABSTRACT

Background: The largest open reading frame in the Saccharomyces genome encodes midasin (MDN1p, YLR106p), an AAA ATPase of 560 kDa that is essential for cell viability. Orthologs of midasin have been identified in the genome projects for Drosophila, Arabidopsis, and Schizosaccharomyces pombe.

Results: Midasin is present as a single-copy gene encoding a well-conserved protein of approximately 600 kDa in all eukaryotes for which data are available. In humans, the gene maps to 6q15 and encodes a predicted protein of 5596 residues (632 kDa). Sequence alignments of midasin from humans, yeast, Giardia and Encephalitozoon indicate that its domain structure comprises an N-terminal domain (35 kDa), followed by an AAA domain containing six tandem AAA protomers (approximately 30 kDa each), a linker domain (260 kDa), an acidic domain (approximately 70 kDa) containing 35-40% aspartate and glutamate, and a carboxy-terminal M-domain (30 kDa) that possesses MIDAS sequence motifs and is homologous to the I-domain of integrins. Expression of hemagglutamin-tagged midasin in yeast demonstrates a polypeptide of the anticipated size that is localized principally in the nucleus.

Conclusions: The highly conserved structure of midasin in eukaryotes, taken in conjunction with its nuclear localization in yeast, suggests that midasin may function as a nuclear chaperone and be involved in the assembly/disassembly of macromolecular complexes in the nucleus. The AAA domain of midasin is evolutionarily related to that of dynein, but it appears to lack a microtubule-binding site.

No MeSH data available.


Tree of sequence relatedness for the six AAA protomers in midasin from humans, yeast and Giardia Asterisks indicate nodes supported with a bootstrap probability of 95% or better, plus signs indicate nodes with probability of 75–95%. The tree was calculated from the multiple alignment in Fig. 3.
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Figure 4: Tree of sequence relatedness for the six AAA protomers in midasin from humans, yeast and Giardia Asterisks indicate nodes supported with a bootstrap probability of 95% or better, plus signs indicate nodes with probability of 75–95%. The tree was calculated from the multiple alignment in Fig. 3.

Mentions: Phylogenetic analysis of the sequence differences between the six protomers in the AAA-domain of midasin (Fig. 4) shows that the evolutionary distance between any two protomers in a single organism is substantially greater than that between any single protomer taken from different organisms, even for such highly disparate organisms as humans and Giardia. This analysis also indicates that the odd-numbered protomers, AAA3 and AAA5, and the even numbered protomers, AAA2, and AAA4, form two separate groups in which, regardless of the organism they come from, the members in any one group are more closely related to each other than they are to any members of the other group.


Expression and genomic analysis of midasin, a novel and highly conserved AAA protein distantly related to dynein.

Garbarino JE, Gibbons IR - BMC Genomics (2002)

Tree of sequence relatedness for the six AAA protomers in midasin from humans, yeast and Giardia Asterisks indicate nodes supported with a bootstrap probability of 95% or better, plus signs indicate nodes with probability of 75–95%. The tree was calculated from the multiple alignment in Fig. 3.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC117441&req=5

Figure 4: Tree of sequence relatedness for the six AAA protomers in midasin from humans, yeast and Giardia Asterisks indicate nodes supported with a bootstrap probability of 95% or better, plus signs indicate nodes with probability of 75–95%. The tree was calculated from the multiple alignment in Fig. 3.
Mentions: Phylogenetic analysis of the sequence differences between the six protomers in the AAA-domain of midasin (Fig. 4) shows that the evolutionary distance between any two protomers in a single organism is substantially greater than that between any single protomer taken from different organisms, even for such highly disparate organisms as humans and Giardia. This analysis also indicates that the odd-numbered protomers, AAA3 and AAA5, and the even numbered protomers, AAA2, and AAA4, form two separate groups in which, regardless of the organism they come from, the members in any one group are more closely related to each other than they are to any members of the other group.

Bottom Line: Expression of hemagglutamin-tagged midasin in yeast demonstrates a polypeptide of the anticipated size that is localized principally in the nucleus.The highly conserved structure of midasin in eukaryotes, taken in conjunction with its nuclear localization in yeast, suggests that midasin may function as a nuclear chaperone and be involved in the assembly/disassembly of macromolecular complexes in the nucleus.The AAA domain of midasin is evolutionarily related to that of dynein, but it appears to lack a microtubule-binding site.

View Article: PubMed Central - HTML - PubMed

Affiliation: Molecular and Cell Biology Department, University of California Berkeley, 94720-3200, USA. joangarb@uclink4.berkeley.edu

ABSTRACT

Background: The largest open reading frame in the Saccharomyces genome encodes midasin (MDN1p, YLR106p), an AAA ATPase of 560 kDa that is essential for cell viability. Orthologs of midasin have been identified in the genome projects for Drosophila, Arabidopsis, and Schizosaccharomyces pombe.

Results: Midasin is present as a single-copy gene encoding a well-conserved protein of approximately 600 kDa in all eukaryotes for which data are available. In humans, the gene maps to 6q15 and encodes a predicted protein of 5596 residues (632 kDa). Sequence alignments of midasin from humans, yeast, Giardia and Encephalitozoon indicate that its domain structure comprises an N-terminal domain (35 kDa), followed by an AAA domain containing six tandem AAA protomers (approximately 30 kDa each), a linker domain (260 kDa), an acidic domain (approximately 70 kDa) containing 35-40% aspartate and glutamate, and a carboxy-terminal M-domain (30 kDa) that possesses MIDAS sequence motifs and is homologous to the I-domain of integrins. Expression of hemagglutamin-tagged midasin in yeast demonstrates a polypeptide of the anticipated size that is localized principally in the nucleus.

Conclusions: The highly conserved structure of midasin in eukaryotes, taken in conjunction with its nuclear localization in yeast, suggests that midasin may function as a nuclear chaperone and be involved in the assembly/disassembly of macromolecular complexes in the nucleus. The AAA domain of midasin is evolutionarily related to that of dynein, but it appears to lack a microtubule-binding site.

No MeSH data available.