This is the N-terminal domain of Rrp40 of the exosome complex present in Saccharomyces cerevisiae. The RNA exosome complex is responsible for degrading RNA molecules in the 3' to 5' direction. Rrp40 is a 'cap' protein and binds the RNase PH barrel on the opposite side from the S1/KH ring. The N-terminal domain of Rrp44 forms a long beta-hairpin that is wedged in between Rrp41-Rrp42 and approaches the N terminus of the cap protein Rrp4 [1]. This domain adopts a beta- sandwich hybrid structure.

1: Crystal structure of an RNA-bound 11-subunit eukaryotic exosome complex. Makino DL, Baumgartner M, Conti E; Nature. 2013;495:70-75. PMID:23376952