Sequence alignment of human RCC1 and putative Arabidopsis homologues (class V). The secondary structures are adapted from solved structure of human RCC1 with minor modifications . Residues absolutely conserved within the secondary structures are black on a colored background. Residues moderately conserved within the secondary structures and/or among Arabidopsis repeats and not human RCC1 are white on a colored background. Boxed residues correspond to amino acids which are highly conserved among each blade of the seven propeller structure .