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The physiological role of ADP and M g 2+ in maintaining a stable beat cycle in bull sperm
Author(s) -
Lindemann Charles B.,
dePinho Tania G.,
Lesich Kathleen A.
Publication year - 2014
Publication title -
cytoskeleton
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 86
eISSN - 1949-3592
pISSN - 1949-3584
DOI - 10.1002/cm.21200
Subject(s) - dynein , flagellum , sperm , biology , beat (acoustics) , adenosine triphosphate , biophysics , microtubule , atp hydrolysis , microbiology and biotechnology , adenosine diphosphate , dynein atpase , biochemistry , enzyme , physics , atpase , platelet , genetics , platelet aggregation , acoustics , immunology , gene
Sperm flagella derive their motive power from the motor protein dynein. In this study, we show that maintenance of the flagellar beat cycle in detergent‐extracted bull sperm models is highly dependent on the ratio of Mg 2+ to adenosine triphosphate (ATP). An excess of either ATP un‐complexed with Mg 2+ , or an excess of Mg 2+ without an equivalent concentration of ATP, results in the loss of beat amplitude and a reduced curvature development in the beat cycle. In addition, we find that adenosine diphosphate (ADP) can stabilize the beat cycle and permit rhythmic beating across a broader range of ATP and Mg 2+ concentrations. We provide evidence that suggests that when ATP is un‐complexed with Mg 2+ , it disrupts the beat cycle by reducing dynein adhesion and thereby, reduces the transmission of dynein‐generated force between the doublets. Excess Mg 2+ does not act by the same mechanism and induces a condition where the flagellum is more resistant to bending. This is consistent with the idea that high Mg 2+ stabilizes rigor bridges, and ATP reduces the microtubule binding affinity of dynein. Our results may explain how intact sperm are able to sustain coordinated flagellar beating under a wide range of metabolic conditions, as intact sperm produce ADP in direct proportion to their consumption of ATP. © 2014 Wiley Periodicals, Inc.