Reply to Heck et al.: Signal amplification at the rhodopsin-to-transducin·phosphodiesterase step in rod phototransduction

In PNAS (1), we estimate ∼12–14 active transducin·phosphodiesterase complexes (GT\*·PDE\*s) produced per active rhodopsin (Rho*) in mouse rods. This is the effective gain—more informative by not including the empty gain from GT*s failing to activate PDE. Nearly all previous estimates were on the total number of GT* produced per Rho* merely because no one before us could measure the individual GT\*·PDE\*-triggered electrical event for direct comparison with the single-Rho* response. We do not state in our paper that previous measurements of the rate of GT* production per Rho* were all incorrect, but rather they spanned a wide range of values with no consensus … [↵][1]1To whom correspondence should be addressed. Email: kwyau{at}jhmi.edu. [1]: #xref-corresp-1-1