The band 3-rich membrane of llama erythrocytes: Studies on cell shape and the organization of membrane proteins

Abstract

The erythrocyte membrane of the llama was characterized in comparison to that of the human. The llama erythrocyte was an elliptical disk that resisted shape alterations in hyperosmotic buffers and following metabolic depletion, both of which induce speculation of the human red cell. Lysophosphatidylcholine incorporation produced minor serrations of the edge of the llama disk but no spicules, whereas human red cells became sphero-echinocytes. The polypeptide profiles in the membranes of the two species were similar, except for several noteworthy differences: a marked elevation in the relative content of band 3; the absence of membrane-bound band 6; and simpler glycoprotein pattern in the llama. The concentration of band 3 in llama was about two and a half to three times that in the human and intramembrane particles in the protoplasmic leaflet of freeze-fractured llama membrane were correspondingly increased. The selective solubilization of bands 1, 2 and 5 in low ionic strength buffer, and all of the peripheral proteins in high alkaline buffer were similar except for increased retention of ankyrin by the llama membrane. These data suggest a similar disposition of membrane proteins. The llama membrane was markedly resistant to the solubilization of integral proteins by the nonionic detergent, Triton X-100. This property and the general resistance to shape changes may be related to the high concentration of band 3.

The Clinicopathologic, Light, and Scanning Electron Microscopic Features of Eperythrozoonosis in Four Naturally Infected Llamas

“…Blood collected into tubes containing EDTA was fixed in glutaraldehyde and prepared by standard techniques for examination by scanning electron microscopy. l 9 Serum iron and total iron binding capacity was determined by potentiometry using a Ferrochem I1 Analyzer (Environmental Sciences Associates, Inc., Bedford, MA). Percent transfenin saturation was calculated by dividing serum iron Tables 2 and 3 indicate the number of days before or after the first observation ofEperythrozoon that the sample was collected and analyzed.…”

The erythrocyte cytoskeleton protein 4.2 is not demonstrable in several mammalian species

“…In general, mammals present small variations in erythrocyte membrane protein concentration as well as in molecular weight (2). Variable spectrin and ankyrin concentrations have been reported in mice (3)(4)(5)(6)(7)(8), as well as a molecular weight variation of band 3 in non-human primates (9), its enrichment in llamas (10), and the absence of band 6 in rats and mice (11,12).…”

The existence of non-axisymmetric bilayer vesicle shapes predicted by the bilayer couple model

“…Experimental observations do, however, also show non-axisymmetric shapes. Cells having elliptical symmetry were found in the blood of some animals, such as the llama (Khodadad and Weinstein 1983) and in the blood of patients with some hereditary disorders of membrane structure and function (Palek 1987). It was also observed by Hotani (1984) that the shapes of the vesicles prepared from phospholipids and cholesterol exhibit axial as well as polygonal symmetries with n = 2, 3, 4 as the vesicle top view is correspondingly deformed from the circle.…”

“…Such shapes are referred to as elliptical. Elliptical shapes were chosen because elliptical erythrocytes were observed experimentally (Palek 1987;Khodadad and Weinstein 1983) and because the calculated equilibrium shapes of nearly spherical vesicles are elliptical (Heinrich et al 1992). For the side view contour, a parametric approach is employed by using the Cassini function (determined by three characteristic parameters) which qualitatively corresponds to the observed shapes for the conditions we are considering (Canham 1970).…”