Research article summary (published 27 Sep 2009):

Membrane-induced conformational change of alpha1-acid glycoprotein characterized by vacuum-ultraviolet circular dichroism spectroscopy.

Full Abstract

The tertiary structure of alpha1-acid glycoprotein (AGP) remains unresolved despite its novel function because AGP is a hard target in X-ray and NMR analyses. To elucidate the membrane-induced conformational change of AGP, the vacuum-ultraviolet circular dichroism (VUVCD) spectra of AGP and its constituent sugars were measured down to 160 nm in the presence or absence of phosphoglyceride liposome using a synchrotron-radiation VUVCD spectrophotometer. The secondary-structure contents and numbers of segments of AGP were estimated from the VUVCD spectra of the protein moiety obtained by subtracting the contributions of the glycan moiety. Further, the positions of secondary structures on the amino acid sequence were predicted by combining the VUVCD data with a neural network algorithm. These comprehensive secondary-structure analyses revealed that AGP consists of 11.4% alpha-helices (3 segments) and 39.9% beta-strands (12 segments) in the absence of liposome (pH 4.5), which are close to the proportions in the secondary structure of native AGP (pH 7.4) predicted by homology modeling, and that it consists of 47.5% alpha-helices (7 segments) and 2.7% beta-strands (2 segments) in the presence of liposome (pH 4.5). Detailed characterization of these alpha-helices of AGP bound to liposome suggested that two alpha-helices (residues 15-27 and 161-175) in the N- and C-terminal regions strongly interact with liposome. Most of the progesterone-binding residues of AGP were involved in the sequences transferring from beta-strands to alpha-helices or unordered structures, which coincided with the large decrease in progesterone-binding capacity of liposome-bound AGP. These results provide the first sequence-level information on the membrane-binding mechanism and structure-function relationship of AGP.

Author information

Author/s: Matsuo, Koichi (K); Namatame, Hirofumi (H); Taniguchi, Masaki (M); Gekko, Kunihiko (K);

Affiliation: Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan.

Journal and publication information

Publication Type: In Vitro; Journal Article; Research Support, Non-U.S. Gov't

Journal: Biochemistry (Biochemistry), published in United States. (Language: eng)

Reference: 2009-Sep; vol 48 (issue 38) : pp 9103-11

Dates: Created 2009/09/22; Completed 2009/10/09;

PMID: 19702310, status: MEDLINE (last retrieval date: 10/9/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Algorithms Amino Acid Sequence Binding Sites Circular Dichroism - methods Humans Hydrogen-Ion Concentration Liposomes - chemistry Models, Molecular Molecular Sequence Data Neural Networks (Computer)

Neural Networks (Computer) Orosomucoid - chemistry; metabolism Phosphatidylglycerols - chemistry Polysaccharides - chemistry Progesterone - metabolism Protein Conformation Protein Structure, Secondary Protein Structure, Tertiary Spectrophotometry, Ultraviolet Vacuum

Associated Chemicals: Liposomes (0) ; Orosomucoid (0) ; Phosphatidylglycerols (0) ; Polysaccharides (0) ; Progesterone (57-83-0)

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