Figure 2. Sequence Alignment of GUN4 and GUN4-like Proteins.

(A) Alignment of the N-terminal portions of GUN4 family members whose N-terminal domains show sequence homology to SynGUN4. Residues contributing to the hydrophobic core of the five-helix bundle are highlighted (pink). GUN4 sequences isolated from plants thus far all have a plastid transit peptide in place of the N-terminal domain found in SynGUN4. The Chlamydomonas reinhardtii sequence was derived from sequence data produced by the United States Department of Energy Joint Genome Institute (http://www.jgi.doe.gov/). The N-terminal sequence of C. reinhardtii is not yet known but it most likely contains a chloroplast transit peptide.

(B) Sequence alignment of possible GUN4 core domains. Residues that form the “palm” of the “cupped hand” are highlighted in pink. Residues from the α6/α7 loop that structure the loop and protrude into the core are highlighted in yellow. Arg214 and Arg217, predicted to be important for binding to porphyrins, are highlighted in blue. Residues that disrupt proper folding when mutated and expressed in E. coli are denoted by an asterisk (*).