Review of 'Interactions between the transmembrane domains of CD39: identification of interacting residues by yeast selection.'

Data are presented from yeast selection experiments to address inter-helical contact amino acids of the two transmembrane domains (TMDs) of CD39 relevant for the function of the protein. CD39 hydrolyzes nucleoside tri- and diphosphates and dynamics of the TMDs seem to be essential for enzymatic activity. Experimental results are transferred into helical wheal projections.

The experimental procedure is properly done and the analysis of the data is sound.

Some minor points:

Page 5: second column, first paragraph: It is written about the findings using ΔTM1CD39 and referred to figure 2. But in this figure it is not obvious which curve relates to ΔTM1CD39. Making the naming consistent would help to read the manuscript.

There is a large bit of very detailed discussion but the overall view is hard to grasp. It is e.g. hard to envision the mutations being done. A graph showing the TMDs as rods and indicating the mutations would be helpful to get a grasp of the idea behind the amino acids selected for mutation.