This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.107.112771v1 93/10/3515    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Luo, X. Articles by Kirschner, D. A. Search for Related Content PubMed PubMed Citation Articles by Luo, X. Articles by Kirschner, D. A.

Cytoplasmic Domain of Zebrafish Myelin Protein Zero: Adhesive Role Depends on β-Conformation

XiaoYang Luo ^*, Hideyo Inouye ^*, Abby A. R. Gross ^*, Marla M. Hidalgo ^*, Deepak Sharma ^*, Daniel Lee ^*, Robin L. Avila ^*, Mario Salmona  and Daniel A. Kirschner ^*

^* Department of Biology, Boston College, Chestnut Hill, Massachusetts; and Department of Molecular Biochemistry and Pharmacology, Istituto di Ricerche Farmacologiche "Mario Negri", Milan, Italy

Correspondence: Address reprint requests to D. A. Kirschner, Biology Department, Boston College, 140 Commonwealth Ave., Higgins Hall, Chestnut Hill, MA 02467-3811. Tel.: 617-552-0211; Fax: 617-552-2011; E-mail: kirschnd{at}bc.edu.

Solution spectroscopy studies on the cytoplasmic domain of human myelin protein zero (P0) (hP0-cyt) suggest that H-bonding between β-strands from apposed molecules is likely responsible for the tight cytoplasmic apposition in compact myelin. As a follow-up to these findings, in the current study we used circular dichroism and x-ray diffraction to analyze the same type of model membranes previously used for hP0-cyt to investigate the molecular mechanism underlying the zebrafish cytoplasmic apposition. This space is significantly narrower in teleosts compared with that in higher vertebrates, and can be accounted for in part by the much shorter cytoplasmic domain in the zebrafish protein (zP0-cyt). Circular dichroism measurements on zP0-cyt showed similar structural characteristics to those of hP0-cyt, i.e., the protein underwent a β structural transition at lipid/protein (L/P) molar ratios >50, and adopted a β-conformation at lower L/P molar ratios. X-ray diffraction was carried out on lipid vesicle solutions with zP0-cyt before and after dehydration to study the effect of protein on membrane lipid packing. Solution diffraction revealed the electron-density profile of a single membrane bilayer. Diffraction patterns of dried samples suggested a multilamellar structure with the β-folded P0-cyt located at the intermembrane space. Our findings support the idea that the adhesive role of P0 at the cytoplasmic apposition in compact myelin depends on the cytoplasmic domain of P0 being in the β-conformation.