Hi All,

I have a question about the directionality information in STRING PPI database. There is a file named protein.actions.v11.0.txt in STRING PPI version 11 and looks like as follows:

item_id_a                 item_id_b                 mode        action      is_directional  a_is_acting  score
10090.ENSMUSP00000000001  10090.ENSMUSP00000000153  binding                 f               f            901
10090.ENSMUSP00000000001  10090.ENSMUSP00000000369  activation  activation  f               f            155
10090.ENSMUSP00000000001  10090.ENSMUSP00000000574  activation  activation  f               f            843
10090.ENSMUSP00000000001  10090.ENSMUSP00000000574  binding                 f               f            921
10090.ENSMUSP00000000001  10090.ENSMUSP00000000574  catalysis               t               f            921
10090.ENSMUSP00000000001  10090.ENSMUSP00000000574  catalysis               t               t            921
10090.ENSMUSP00000000001  10090.ENSMUSP00000000574  reaction                f               f            921
10090.ENSMUSP00000000001  10090.ENSMUSP00000000574  reaction                t               f            921

In this file, there are two fields for denoting the regulation, named is_directional and a_is_acting. There is some information about a_is_acting field but not about is_directional field. My question is that if is_directional is TRUE, does that mean either protein is regulated by the other?

For example, for the 6th and 8th (last) interaction listed above, as is_directional is TRUE and a_is_acting is FALSE, can we conclude that protein_b regulates protein_a?