title: Signature amino acids enable the archaeal L7Ae box C/D RNP core protein to recognize and bind the K-loop RNA motif.
abstract: The archaeal L7Ae and eukaryotic 15.5kD protein homologs are members of the L7Ae/15.5kD protein family that characteristically recognize K-turn motifs found in both archaeal and eukaryotic RNAs. In Archaea, the L7Ae protein uniquely binds the K-loop motif found in box C/D and H/ACA sRNAs, whereas the eukaryotic 15.5kD homolog is unable to recognize this variant K-turn RNA. Comparative sequence and structural analyses, coupled with amino acid replacement experiments, have demonstrated that five amino acids enable the archaeal L7Ae core protein to recognize and bind the K-loop motif. These signature residues are highly conserved in the archaeal L7Ae and eukaryotic 15.5kD homologs, but differ between the two domains of life. Interestingly, loss of K-loop binding by archaeal L7Ae does not disrupt C'/D' RNP formation or RNA-guided nucleotide modification. L7Ae is still incorporated into the C'/D' RNP despite its inability to bind the K-loop, thus indicating the importance of protein-protein interactions for RNP assembly and function. Finally, these five signature amino acids are distinct for each of the L7Ae/L30 family members, suggesting an evolutionary continuum of these RNA-binding proteins for recognition of the various K-turn motifs contained in their cognate RNAs.
authors.affiliation: Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: Keith T
authors.initials: KT
authors.lastname: Gagnon
authors.forename: Xinxin
authors.initials: X
authors.lastname: Zhang
authors.forename: Guosheng
authors.initials: G
authors.lastname: Qu
authors.forename: Shyamasri
authors.initials: S
authors.lastname: Biswas
authors.forename: Jimmy
authors.initials: J
authors.lastname: Suryadi
authors.forename: Bernard A
authors.initials: BA
authors.lastname: Brown
authors.forename: E Stuart
authors.initials: ES
authors.lastname: Maxwell
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000595:Amino Acid Sequence; D001105:Archaea / Q000235:genetics / Q000378:metabolism; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D017124:Conserved Sequence; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D011485:Protein Binding / Q000235:genetics; D019642:RNA, Archaeal / Q000737:chemistry* / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D019843:Archaeal Proteins; D019642:RNA, Archaeal; D012261:Ribonucleoproteins