My take on the basic riff is as follows:

e---------3-------
B-----2-5---5-2-5-
G-2-2-------------
D-----------------
A-----------------
E-----------------

This is the riff in A. You just move the same shape up the neck to follow the standard blues progression:
A / D / A / E / D / A / E.

When you get back to the A before the final E, the riff is:


e-----5-
B-----5-
G-7b9--- (repeat)
D-------
A-------
E-------

Then you do an E7 and start back at the beginning.