One of the very few “minor” grooves we find in the Chicago blues style.

Magic Sam was the one who played these types of grooves.
The groove on the I chord is minor, but what’s happening with the IV and V?

Magic Sam would use a very open sounding voicing for these chords.
They don’t have a third!

Approach them as major chords and, although officially you can’t call them major or minor, they are written as major chords.