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J Cell Biol

Title:		Identification and initial characterization of an autocrine pheromone receptor in the protozoan ciliate Euplotes raikovi
Author(s):		Ortenzi C; Miceli C; Bradshaw RA; Luporini P;
Address:		"Department of Cell Biology, University of Camerino, Italy"
Journal Title:		J Cell Biol
Year:		1990
Volume:		111
Issue:		2
Page Number:		607 - 614
DOI:		10.1083/jcb.111.2.607
ISSN/ISBN:		0021-9525 (Print) 1540-8140 (Electronic) 0021-9525 (Linking)
Abstract:		"The polypeptide pheromone Er-1, purified from the ciliate Euplotes raikovi of mating type I and genotype mat-1/mat-1, was iodinated with 125I-Bolton-Hunter reagent to a sp act of 0.45-0.73 mu Ci/microgram of protein. This preparation of 125I-Er-1 bound specifically to high affinity binding sites on the same cells of mating type I. Binding of 125I-Er-1 occurred with an apparent Kd of 4.63 +/- 0.12 X 10(-9) M in cells in early stationary phase. It was estimated that these cells carry a total number of approximately 5 X 10(7) sites/cell, with a site density that falls in the range of 1,600-1,700/microns 2 of cell surface. Unlabeled Er-1, other homologous pheromones such as Er-2 and Er-10, antibodies specific for Er-1, and human IL-2 were shown to act as effective inhibitors of specific binding of 125I-Er-1 to mating type I cells. The 'autocrine' nature of the identified specific high affinity binding sites for Er-1 was further substantiated by cross-linking experiments. These experiments revealed that mating type-I cell membranes contain one protein entity of Mr = 28,000 that is capable of reacting specifically with the homodimeric native form of Er-1"
Keywords:		"Animals Binding, Competitive Ciliophora/*physiology Electrophoresis, Polyacrylamide Gel Kinetics *Membrane Proteins Molecular Weight Peptides/*metabolism Pheromones/metabolism *Protozoan Proteins Receptors, Cell Surface/biosynthesis/isolation & purificati;"
Notes:		"MedlineOrtenzi, C Miceli, C Bradshaw, R A Luporini, P eng DK 32456/DK/NIDDK NIH HHS/ Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. 1990/08/01 J Cell Biol. 1990 Aug; 111(2):607-14. doi: 10.1083/jcb.111.2.607"