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ATP hydrolysis coupled to microtubule sliding in sea-urchin sperm flagella
Abstract:
Using sea urchin (Hemicentrotus pulcherimus) sperm flagella, ATP hydrolysis coupled to sliding movement of microtubules was investigated. Flagellar axonemes were pretreated with trypsin and the microtubules induced to slide by addition of ATP (50-1,000 microM) at 0-20 degrees C. Motion-dependent hydrolysis of ATP was observed immediately after the addition of ATP, the rate of which was higher than that of steady state hydrolysis in axonemes without trypsin-treatment, or after complete disintegration. The rate of hydrolysis of ATP divided by the sliding velocity of microtubules reflects the ATP consumption necessary per unit distance of microtubule sliding. This parameter varied according to the experimental conditions in that it increased when the ATP concentration or temperature was decreased. Our results suggest that there is not a strict stoichiometric relationship between ATP hydrolysis and sliding distance in the dynein-tubulin system, indicating that the mechanochemical coupling is different from that in beating axonemes.
Insights
Researchers studied how ATP hydrolysis powers microtubule sliding in sea urchin sperm flagella. They found the relationship between ATP use and sliding distance is not strictly fixed, suggesting unique mechanochemical coupling in this system.
Area of Science:
- Biochemistry
- Cell Biology
- Biophysics
Background:
- Sea urchin sperm flagella utilize adenosine triphosphate (ATP) hydrolysis for motility.
- Microtubule sliding within flagellar axonemes is the basis for flagellar movement.
- Understanding the mechanochemical coupling of ATP hydrolysis to microtubule sliding is crucial for cell motility research.
Purpose of the Study:
- To investigate the relationship between ATP hydrolysis and microtubule sliding velocity in sea urchin sperm flagella.
- To determine the ATP consumption per unit distance of microtubule sliding under varying conditions.
- To elucidate the nature of mechanochemical coupling in the dynein-tubulin system.
Main Methods:
- Preparation of flagellar axonemes from Hemicentrotus pulcherimus sperm.
- Trypsin pretreatment of axonemes to induce microtubule sliding.
- Addition of varying concentrations of ATP (50-1,000 microM) at temperatures ranging from 0-20 degrees C.
- Measurement of ATP hydrolysis rates and microtubule sliding velocities.
Main Results:
- Motion-dependent ATP hydrolysis was observed immediately upon ATP addition.
- The rate of ATP hydrolysis was higher in trypsin-treated axonemes compared to untreated or disintegrated axonemes.
- The ratio of ATP hydrolysis rate to sliding velocity (ATP consumption per unit distance) varied with ATP concentration and temperature, increasing at lower values.
- A non-stoichiometric relationship between ATP hydrolysis and microtubule sliding distance was observed.
Conclusions:
- The dynein-tubulin system in sea urchin sperm flagella does not exhibit a strict stoichiometric coupling between ATP hydrolysis and microtubule sliding distance.
- Mechanochemical coupling in this system appears to differ from that observed in beating axonemes.
- These findings provide insights into the complex energy transduction mechanisms underlying flagellar motility.