HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) 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 Mather, I. H. Articles by Keenan, T. W. Search for Related Content PubMed PubMed Citation Articles by Mather, I. H. Articles by Keenan, T. W.

Membranes of Mammary Gland. XII. Loosely Associated Proteins and Compositional Heterogeneity of Bovine Milk Fat Globule Membrane

Department of Animal Sciences, Purdue University, West Lafayette, IN 47907

ABSTRACT

Electrophoretic patterns of polypeptides of milk fat globule differed quantitatively depending on extent of washing during membrane preparation. This was due to selective loss of loosely associated, extrinsic membrane proteins. Major polypeptides with apparent molecular weights of 155,000 and 43,500 and membrane glycoproteins were released selectively during preparation of milk fat globule membranes. Evidence suggested that xanthine oxidase was a constituent of the selectively removed polypeptide fraction of apparent molecular weight 155,000. A major class of polypeptide with an apparent molecular weight of 62,500 was not extracted from milk fat globule membrane by treatment with dilute salts, ethylenediaminetetraacetic acid, or by nonionic and ionic detergent solutions. Milk fat globule membranes were separated into seven subfractions on isopycnic centrifugation in sucrose density gradients. Specific activities of the enzymes 5' -nucleotidase, xanthine oxidase, acid and alkaline phosphatases were similar or identical in all fractions. Electrophoretic analysis showed these seven subfractions had similar polypeptide profiles. Both phospholipid and total lipid content of subfractions were correlated inversely with fraction density. The results show that milk fat globule membrane is nearly homogenous in content of intrinsic membrane proteins and certain membrane

¹ Department of Dairy Science, University of Maryland, College Park 20742.

² Cooperative project with the Division of Membrane Biology and Biochemistry, Institute of Experimental Pathology, German Cancer Research Center, Heidelberg, Federal Republic of Germany.