Great track, based on minor 1-3-5 line with a run coming under it again from the dom 5 as a lead to the root again.
using E as the root that is E-G-A-G-A then the run under it B-D-D#-E.
This is the "meat and potatoes" of the song or should i say this take. To get the feel for it don't try and reproduce it exact..as said it is a take,
Willie would have changed it when he played it but stayed within the "spirit of the original recording".
I would listen to more of how Willie plays to get a feel for his "spirit" and then use that in the playing.
He will move of and around this shape in timing and rhythm, but will infer it in the playing, a trick of Willies. He would infer things for you to hear that were not in his playing alone, but using other players playing to compliment a new sound or feeling, but it sounded like it came from the bass. LOL sound quality of the day helped with this.
Great place to start is Willie Dixons Blues Dixonary box set, it has the great man from start to finish and essential listening for any blues player IMO
