Meaning of の in this sentence


The sentence is

> それがいかなる彼女の琴線に触れたのかはわからない

I believe that かは is embedding the question (as seen
[here](https://japanese.stackexchange.com/questions/61495/what-
does-%e3%81%8b%e3%81%af-mean)) but I'm a little confused at what role の is
playing here. Is it simply nominalizing the previous sentence? and if so why
is it playing this role?

