You can try to turn off/on the USB hub controller with below commands on C1 via controlling the reset pin of the USB hub IC on the C1 board. It will disable the 5V output too. Note that it will disable all 4 host ports. There is no way to control the port individually.
Thank you for your quick answer. That works perfectly fine for my application. My last quastion would be: Where did you find this information. Is there any kind of documentation for this kind of information?