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Sea urchin sperm respond to egg factors with changes in the ionic permeability of their plasma membrane. It has been previously shown that plasma membranes isolated preferentially from sea urchin sperm flagella respond to egg jelly increasing their Ca2+ and Na+ uptake (Darszon et al. (1984) Eur. J. Biochem. 144, 515-522). However, the egg jelly induced acrosome reaction occurs in the sperm head, and there is evidence for an heterogeneous distribution of plasma membrane components within the various regions of this cell. We here report a method for purifying sperm head membranes using positively charged beads according to Jacobson (1977) Biochim. Biophys. Acta 471, 331-335). Under the transmission electron microscope these membranes appeared homogeneous and apparently free of internal membranes. The yield of the preparation was 0.9% of the total protein in the sperm homogenate. The preparation contained less than 5% of the mitochondrial marker cytochrome oxidase, and 10% of the total DNA/mg protein. Surface labeling with 125I indicated a 2.5-3-fold enrichment in specific activity of the head membranes with respect to whole sperm. The SDS band pattern and the lipid composition of this preparation were different from those of isolated flagellar membranes. Phosphatidylcholine was higher in the head membranes, while phosphatidylserine and phosphatidylethanolamine were lower. The head membranes displayed a 1.7-2.3-fold higher Ca2+-ATPase activity and a 2.5-fold lower Na+/K+-ATPase activity, than the flagellar membranes. These results are consistent with a heterogeneous distribution of membrane components along the sea urchin sperm plasma membranes. Isolated head membranes sonicated in the presence of soybean phospholipid liposomes responded to egg jelly with a species-specific increase in Ca2+ and Na+ uptake. As in whole sperm, Ca2+ uptake was inhibited by the Ca2+ channel blocker nisoldipine. A close analog of this compound, [3H]nitrendipine, binds with high affinity to head membranes in a saturable, reversible manner, showing a Kd and Bmax of 31 nM and 5.3 pmol/mg protein, respectively.
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
November 1984,
European journal of biochemistry,
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
July 1983,
Developmental biology,
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
August 1985,
Developmental biology,
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
January 2004,
Methods in molecular biology (Clifton, N.J.),
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
October 1980,
Developmental biology,
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
November 1989,
The Journal of biological chemistry,
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
January 1984,
Development, growth & differentiation,
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
June 1987,
FEBS letters,
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
September 1983,
Proceedings of the National Academy of Sciences of the United States of America,
J García-Soto, and
M Mourelle, and
I Vargas, and
L de De la Torre, and
E Ramírez, and
A M López-Colomé, and
A Darszon
February 1990,
The Journal of general physiology,
