title: Liaison between myristoylation and cryptic EF-hand motif confers Ca(2+) sensitivity to neuronal calcium sensor-1.
abstract: Many members of the neuronal calcium sensor (NCS) protein family have a striking coexistence of two characteristics, that is, N-myristoylation and the cryptic EF-1 motif. We investigated the rationale behind this correlation in neuronal calcium sensor-1 (NCS-1) by restoring Ca(2+) binding ability of the disabled EF-1 loop by appropriate mutations. The concurrence of canonical EF-1 and N-myristoylation considerably decreased the overall Ca(2+) affinity, conformational flexibility, and functional activation of downstream effecter molecules (i.e., PI4Kβ). Of a particular note, Ca(2+) induced conformational change (which is the first premise for a CaBP to be considered as sensor) is considerably reduced in myristoylated proteins in which Ca(2+)-binding to EF-1 is restored. Moreover, Ca(2+), which otherwise augments the enzymatic activity of PI4Kβ (modulated by NCS-1), leads to a further decline in the modulated PI4Kβ activity by myristoylated mutants (with canonical EF-1) pointing toward a loss of Ca(2+) signaling and specificity at the structural as well as functional levels. This study establishes the presence of the strong liaison between myristoylation and cryptic EF-1 in NCS-1. Breaking this liaison results in the failure of Ca(2+) specific signal transduction to downstream effecter molecules despite Ca(2+) binding. Thus, the EF-1 disability is a prerequisite in order to append myristoylation signaling while preserving structural robustness and Ca(2+) sensitivity/specificity in NCS-1.
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology (CCMB), Hyderabad 500007, India.
authors.forename: Vangipurapu
authors.initials: V
authors.lastname: Rajanikanth
authors.forename: Anand Kumar
authors.initials: AK
authors.lastname: Sharma
authors.forename: Meduri
authors.initials: M
authors.lastname: Rajyalakshmi
authors.forename: Kousik
authors.initials: K
authors.lastname: Chandra
authors.forename: Kandala V R
authors.initials: KV
authors.lastname: Chary
authors.forename: Yogendra
authors.initials: Y
authors.lastname: Sharma
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009227:Myristic Acids / Q000378:metabolism*; D051580:Neuronal Calcium-Sensor Proteins / Q000235:genetics / Q000378:metabolism*; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology
chemical_list: D009227:Myristic Acids; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; C101464:frequenin calcium sensor proteins; D002118:Calcium