Table I

Pharmacological Characterization of Phagosome Motility

ConditionNumber of movements/min/fieldPercent plus end–directed movementsnVelocity (μm/second)
no ATP  0 ± 0NANANA
10 mM MgATP1.17 ± 0.51    18.2331.03 ± 0.31
10 mM MgGTP0.13 ± 0.10100100.38 ± 0.06
10 mM MgATP0.85 ± 0.29   6.531ND
 + 1 mM MgAMP
1 μM VO4+0.79 ± 0.20  30.826ND
10 μM VO4+0.27 ± 0.11  57.121ND
100 μM VO4+      0.17 ± 0.04NDNAND
  • Phagosome motility on polarity-marked microtubules was assayed as described in Materials and Methods; the mean number of movements per minute per video field is given here. Each value represents the mean of the average movements/field/min of at least two, but often many more, identical motility chambers; errors are population standard deviations. Each experiment was independently repeated at least twice, but often many more times. For each point at least two different preparations of cytosol, phagosomes, and nucleotide analogue were tested. The phagosomes used in these experiments were not salt-stripped with 2 M NaCl. For addition of ATP, GTP, and AMP-PNP, cytosol was desalted as described in Blocker et al. (1996). These experiments, with the exception of vanadate addition, were done in the absence of an ATP regenerating system. n = total number of movements of clear polarity per condition; polarity is unambiguous for ∼30% of movements; the percent of plus end–directed movements in the presence of GTP and AMP-PNP is significantly different from that in the ATP control at P = 0.01 and P = 0.10, respectively; in the presence of 10 μM VO4+ the percent of plus end–directed movements is significantly different from that in the nondesalted control (see Results) at P = 0.01, but in the presence of 1 μM VO4+ it is not. In 10 mM MgATP, only the velocity of plus end–directed movements was determined. In 10 mM GTP, the velocity of all movements was determined. Because these movements were slow, image frames were collected at 3-s intervals. Vanadate was prepared as in Kypta et al. (1988). ND, Not determined; NA, Not applicable.