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The N-terminal Region of α-Dystroglycan is an Autonomous Globular Domain


Brancaccio, A; Schulthess, T; Gesemann, M; Engel, J (1997). The N-terminal Region of α-Dystroglycan is an Autonomous Globular Domain. European Journal of Biochemistry, 246(1):166-172.

Abstract

The structure of the N-terminal region of mouse α-dystroglycan (DGN) was investigated by expression of two protein fragments (residues 30–180 and 30–438) in Escherichia coli cells. Trypsin susceptibility experiments show the presence of a stable α-dystroglycan N-terminal region (approximately from residue 30 to 315). In addition, guanidinium hydrochloride (Gdn/HCl) denaturation of DGN-(30–438)-peptide, monitored by means of tryptophan fluorescence, produces a cooperative transition typical of folded protein structures. These results strongly suggest that the α-dystroglycan N-terminal is an autonomous folding unit preluding a flexible mucin-like region and that its folding is not influenced by the absence of glycosylation. In order to obtain more information on the structural features of the N-terminal domain we have also used circular dichroism, analytical sedimentation and electron microscopy analysis. Circular dichroic spectra show the absence of typical secondary structure (e.g. α-helix or β-sheet) and closely resemble those recorded for loop-containing proteins. This is consistent with a sequence similarity of the α-dystroglycan domain with the loop-containing protein elastase. Analytical ultracentrifugation and electron microscopy analysis reveal that the N-terminal domain has a globular structure. DGN-(30–438)-peptide does not bind in the nanomolar range to an iodinated agrin fragment which binds with high affinity to tissue purified α-dystroglycan. No binding was detected also to laminin. This result suggests that the α-dystroglycan N-terminal domain does not contain the binding site to its extracellular matrix binding partners. It is less likely than the lack of glycosylation reduces its binding affinity, because the N-terminal globular domain only contains two glycosylation sites.

The structure of the N-terminal region of mouse α-dystroglycan (DGN) was investigated by expression of two protein fragments (residues 30–180 and 30–438) in Escherichia coli cells. Trypsin susceptibility experiments show the presence of a stable α-dystroglycan N-terminal region (approximately from residue 30 to 315). In addition, guanidinium hydrochloride (Gdn/HCl) denaturation of DGN-(30–438)-peptide, monitored by means of tryptophan fluorescence, produces a cooperative transition typical of folded protein structures. These results strongly suggest that the α-dystroglycan N-terminal is an autonomous folding unit preluding a flexible mucin-like region and that its folding is not influenced by the absence of glycosylation. In order to obtain more information on the structural features of the N-terminal domain we have also used circular dichroism, analytical sedimentation and electron microscopy analysis. Circular dichroic spectra show the absence of typical secondary structure (e.g. α-helix or β-sheet) and closely resemble those recorded for loop-containing proteins. This is consistent with a sequence similarity of the α-dystroglycan domain with the loop-containing protein elastase. Analytical ultracentrifugation and electron microscopy analysis reveal that the N-terminal domain has a globular structure. DGN-(30–438)-peptide does not bind in the nanomolar range to an iodinated agrin fragment which binds with high affinity to tissue purified α-dystroglycan. No binding was detected also to laminin. This result suggests that the α-dystroglycan N-terminal domain does not contain the binding site to its extracellular matrix binding partners. It is less likely than the lack of glycosylation reduces its binding affinity, because the N-terminal globular domain only contains two glycosylation sites.

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Additional indexing

Other titles:The N-terminal region of alpha-dystroglycan is an autonomous globular domain.
Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Brain Research Institute
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:1997
Deposited On:11 Feb 2008 12:12
Last Modified:05 Apr 2016 12:12
Publisher:Wiley-Blackwell
ISSN:0014-2956
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:10.1111/j.1432-1033.1997.00166.x
PubMed ID:9210479
Permanent URL: http://doi.org/10.5167/uzh-127

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