The C-terminal domain of FCP-1 is required for interaction with the carboxy terminal domain of RAP74. Interaction relies extensively on van der Waals contacts between hydrophobic residues situated within alpha-helices in both domains [1].

1: NMR structure of a complex containing the TFIIF subunit RAP74 and the RNA polymerase II carboxyl-terminal domain phosphatase FCP1. Nguyen BD, Abbott KL, Potempa K, Kobor MS, Archambault J, Greenblatt J, Legault P, Omichinski JG; Proc Natl Acad Sci U S A. 2003;100:5688-5693. PMID:12732728