An improved electron density map of lobster holo-n-glyceraldehyde-3-phosphate dehydrogenase has
been computed to 2.9 8, resolution based on two heavy atom isomorphous derivatives. This has been
averaged only over the Q molecular 2-fold axis, which is known to be exact in the human holoenzyme.
The map showed possible asymmetry between the subunits in which the active centers are closely related
across the R axis (that is, between the red and green or between the yellow and blue subunits). A
difference map between the electron density of citrate and sulfate-soaked crystals gave further evidence
for possible asymmetry.
The major differences