Different adhesion inhibiting activities of antisera against plasma membranes of liver and Morris hepatoma 7777

Half-lives and rate constants of degradation of protein-bound fucose have been determined in plasma membranes and total cell homogenates of rat liver and Morris hepatoma 7777. The existence of at least two dynamically different classes of fucose-containing glycoproteins could be demonstrated in both liver and hepatoma plasma membranes. The apparent half-lives were 8.4 and 24.5 h (host liver) and 11.5 and 33.9 h (Morris hepatoma). Since this biphasic loss of fucose residues was not observed for sialic acid [Harms & Reutter (1974) Cancer Res. 34, 3165–3172], the differences are possibly related to specific functions of fucosylated glycoproteins of the plasma membrane.

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On the structural organization of biological pumps and channels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110878 ◽

1984 ◽

Vol 42 ◽

pp. 138-141

Author(s):

G. Zampighi ◽

M. Kreman

Keyword(s):

Active Transport ◽

Transport System ◽

Plasma Membranes ◽

Transport Proteins ◽

Molecular Organization ◽

Passive Transport ◽

Concentration Gradients ◽

Cell Functions ◽

Natural Concentration ◽

Active Transport System

The plasma membranes of most animal cells contain transport proteins which function to provide passageways for the transported species across essentially impermeable lipid bilayers. The channel is a passive transport system which allows the movement of ions and low molecular weight molecules along their concentration gradients. The pump is an active transport system and can translocate cations against their natural concentration gradients. The actions and interplay of these two kinds of transport proteins control crucial cell functions such as active transport, excitability and cell communication. In this paper, we will describe and compare several features of the molecular organization of pumps and channels. As an example of an active transport system, we will discuss the structure of the sodium and potassium ion-activated triphosphatase [(Na+ +K+)-ATPase] and as an example of a passive transport system, the communicating channel of gap junctions and lens junctions.

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Membrane microdomains: lessons from microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140257 ◽

1995 ◽

Vol 53 ◽

pp. 776-777

Author(s):

J.M. Robinson ◽

J.M Oliver

Keyword(s):

Spatial Distribution ◽

Plasma Membrane ◽

Epithelial Cells ◽

Plasma Membranes ◽

Cell Types ◽

Imaging Modalities ◽

Membrane Microdomains ◽

Membrane Domains ◽

Lateral Heterogeneity ◽

Functional Importance

Specialized regions of plasma membranes displaying lateral heterogeneity are the focus of this Symposium. Specialized membrane domains are known for certain cell types such as differentiated epithelial cells where lateral heterogeneity in lipids and proteins exists between the apical and basolateral portions of the plasma membrane. Lateral heterogeneity and the presence of microdomains in membranes that are uniform in appearance have been more difficult to establish. Nonetheless a number of studies have provided evidence for membrane microdomains and indicated a functional importance for these structures.This symposium will focus on the use of various imaging modalities and related approaches to define membrane microdomains in a number of cell types. The importance of existing as well as emerging imaging technologies for use in the elucidation of membrane microdomains will be highlighted. The organization of membrane microdomains in terms of dimensions and spatial distribution is of considerable interest and will be addressed in this Symposium.

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