title: Long-range effects on calcium binding and conformational change in the N-domain of calmodulin.
abstract: Proteins within the EF-hand protein family exhibit different conformational responses to Ca(2+) binding. Calmodulin and other members of the EF-hand protein family undergo major changes in conformation upon binding Ca(2+). However, some EF-hand proteins, such as calbindin D9k (Clb), bind Ca(2+) without a significant change in conformation. Here, we investigate the effects of replacement of a leucine at position 39 of the N-terminal domain of calmodulin (N-Cam) with a phenylalanine derived from Clb. This variant is studied alone and in the context of other mutations that affect the conformational properties of N-Cam. Strikingly, the introduction of Phe39, which is distant from the calcium binding sites, leads to a significant enhancement of Ca(2+) binding affinity, even in the context of other mutations which trap the protein in the closed form. The results yield novel insights into the evolution of EF-hand proteins as calcium sensors versus calcium buffers.
authors.affiliation: Department of Chemistry, 408 Chandlee Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: A
authors.initials: A
authors.lastname: Ababou
authors.forename: R A
authors.initials: RA
authors.lastname: Shenvi
authors.forename: J R
authors.initials: JR
authors.lastname: Desjarlais
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005973:Glutamine / Q000235:genetics; D006801:Humans; D007532:Isoleucine / Q000235:genetics; D007930:Leucine / Q000235:genetics; D008239:Lysine / Q000235:genetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010649:Phenylalanine / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D011487:Protein Conformation; D011489:Protein Denaturation / Q000235:genetics; D017510:Protein Folding; D017434:Protein Structure, Tertiary / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D002147:Calmodulin; D010446:Peptide Fragments; D007532:Isoleucine; D005973:Glutamine; D010649:Phenylalanine; D007930:Leucine; D008239:Lysine; D002118:Calcium