Transposition of two amino acids changes a promiscuous RNA binding protein into a sequence-specific RNA binding protein.
In yeast (Saccharomyces cerevisiae), the branchpoint binding protein (BBP) recognizes the conserved yeast branchpoint sequence (UACUAAC) with a high level of specificity and affinity, while the human branchpoint binding protein (SF1) binds the less-conserved consensus branchpoint sequence (CURAY) in human introns with a lower level of specificity and affinity. To determine which amino acids in BBP provide the additional specificity and affinity absent in SF1, a panel of chimeric SF1 proteins was tested in RNA binding assays with wild-type and mutant RNA substrates. This approach revealed that the QUA2 domain of BBP is responsible for the enhanced RNA binding affinity and specificity displayed by BBP compared with SF1. Within the QUA2 domain, a transposition of adjacent arginine and lysine residues is primarily responsible for the switch in RNA binding between BBP and SF1. Alignment of multiple branchpoint binding proteins and the related STAR/GSG proteins suggests that the identity of these two amino acids and the RNA target sequences of all of these proteins are correlated.
Garrey
Stephen M
SM
Department of Chemistry and Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
Cass
Danielle M
DM
Wandler
Anica M
AM
Scanlan
Mary S
MS
Berglund
J Andrew
JA
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001120:Arginine / Q000737:chemistry; D005454:Fluorescence Polarization; D006801:Humans; D007438:Introns; D008239:Lysine / Q000737:chemistry; D008969:Molecular Sequence Data; D016601:RNA-Binding Proteins / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
D016601:RNA-Binding Proteins; D001120:Arginine; D008239:Lysine