This is helix turn helix domain found in alpha helical region of Rubisco accumulation factor1 (Raf1). Raf1 from Arabidopsis thaliana consists of an N-terminal alpha-domain, a flexible linker segment and a C-terminal beta-sheet domain that mediates dimerization. The alpha-domains mediate the majority of functionally important contacts with RbcL (Rubisco large subunits) by bracketing each RbcL dimer at the top and bottom. The alpha-domain alone is essentially inactive [1].

1: Structure and mechanism of the Rubisco-assembly chaperone Raf1. Hauser T, Bhat JY, Milicic G, Wendler P, Hartl FU, Bracher A, Hayer-Hartl M; Nat Struct Mol Biol. 2015;22:720-728. PMID:26237510