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Title: A 39-kD plasma membrane protein (IP39) is an anchor for the unusual membrane skeleton of Euglena gracilis

The major integral plasma membrane protein (IP39) of Euglena gracilis was radiolabeled, peptide mapped, and dissected with proteases to identify cytoplasmic domains that bind and anchor proteins of the cell surface. When plasma membranes were radioiodinated and extracted with octyl glucoside, 98% of the extracted label was found in IP39 or the 68- and 110-kD oligomers of IP39. The octyl glucoside extracts were incubated with unlabeled cell surface proteins immobilized on nitrocellulose (overlays). Radiolabel from the membrane extract bound one (80 kD) of the two (80 and 86 kD) major membrane skeletal protein bands. Resolubilization of the bound label yielded a radiolabeled polypeptide identical in Mr to IP39. Intact plasma membranes were also digested with papain before or after radioiodination, thereby producing a cytoplasmically truncated IP39. The octyl glucoside extract of truncated IP39 no longer bound to the 80-kD membrane skeletal protein in the nitrocellulose overlays. EM of intact or trypsin digested plasma membranes incubated with membrane skeletal proteins under stringent conditions similar to those used in the nitrocellulose overlays revealed a partially reformed membrane skeletal layer. Little evidence of a membrane skeletal layer was found, however, when plasma membranes were predigested with papain before reassociation. A candidate 80-kD bindingmore » domain of IP39 has been tentatively identified as a peptide fragment that was present after trypsin digestion of plasma membranes, but was absent after papain digestion in two-dimensional peptide maps of IP39. Together, these data suggest that the unique peripheral membrane skeleton of Euglena binds to the plasma membrane through noncovalent interactions between the major 80-kD membrane skeletal protein and a small, papain sensitive cytoplasmic domain of IP39.« less
Authors:
; ;  [1]
  1. (Univ. of Illinois, Chicago (USA))
Publication Date:
OSTI Identifier:
6828350
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cell Biology; (USA); Journal Volume: 110:4
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; MEMBRANE PROTEINS; MOLECULAR STRUCTURE; AUTORADIOGRAPHY; CELL MEMBRANES; CHEMICAL BONDS; ELECTRON MICROSCOPY; EUGLENA; IODINE ISOTOPES; MOLECULAR WEIGHT; PEPTIDE HYDROLASES; PROTEIN STRUCTURE; TRYPSIN; TWO-DIMENSIONAL ELECTROPHORESIS; ALGAE; ANIMALS; CELL CONSTITUENTS; ELECTROPHORESIS; ENZYMES; EUGLENOPHYCOTA; HYDROLASES; INVERTEBRATES; ISOTOPES; MASTIGOPHORA; MEMBRANES; MICROORGANISMS; MICROSCOPY; ORGANIC COMPOUNDS; PLANTS; PROTEINS; PROTOZOA; SERINE PROTEINASES; UNICELLULAR ALGAE 550201* -- Biochemistry-- Tracer Techniques