Document Detail

Structure of androcam supports specialized interactions with myosin VI.
MedLine Citation:
PMID:  22851764     Owner:  NLM     Status:  MEDLINE    
Androcam replaces calmodulin as a tissue-specific myosin VI light chain on the actin cones that mediate D. melanogaster spermatid individualization. We show that the androcam structure and its binding to the myosin VI structural (Insert 2) and regulatory (IQ) light chain sites are distinct from those of calmodulin and provide a basis for specialized myosin VI function. The androcam N lobe noncanonically binds a single Ca(2+) and is locked in a "closed" conformation, causing androcam to contact the Insert 2 site with its C lobe only. Androcam replacing calmodulin at Insert 2 will increase myosin VI lever arm flexibility, which may favor the compact monomeric form of myosin VI that functions on the actin cones by facilitating the collapse of the C-terminal region onto the motor domain. The tethered androcam N lobe could stabilize the monomer through contacts with C-terminal portions of the motor or recruit other components to the actin cones. Androcam binds the IQ site at all calcium levels, constitutively mimicking a conformation adopted by calmodulin only at intermediate calcium levels. Thus, androcam replacing calmodulin at IQ will abolish a Ca(2+)-regulated, calmodulin-mediated myosin VI structural change. We propose that the N lobe prevents androcam from interfering with other calmodulin-mediated Ca(2+) signaling events. We discuss how gene duplication and mutations that selectively stabilize one of the many conformations available to calmodulin support the molecular evolution of structurally and functionally distinct calmodulin-like proteins.
Mehul K Joshi; Sean Moran; Kathleen M Beckingham; Kevin R MacKenzie
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-07-31
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  109     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-08-15     Completed Date:  2012-10-29     Revised Date:  2013-07-12    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  13290-5     Citation Subset:  IM    
Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005, USA.
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MeSH Terms
Amino Acid Sequence
Binding Sites
Calcium Chloride / metabolism
Calcium-Binding Proteins / chemistry*,  metabolism*
Calmodulin / chemistry,  metabolism
Drosophila Proteins / chemistry*,  metabolism*
Drosophila melanogaster / metabolism*
EF Hand Motifs
Glycine / metabolism
Magnetic Resonance Spectroscopy
Models, Molecular
Molecular Sequence Data
Myosin Heavy Chains / chemistry,  metabolism*
Peptides / chemistry,  metabolism
Protein Binding
Protein Structure, Tertiary
Structure-Activity Relationship
Grant Support
Reg. No./Substance:
0/And protein, Drosophila; 0/Calcium-Binding Proteins; 0/Calmodulin; 0/Drosophila Proteins; 0/Myosin Heavy Chains; 0/Peptides; 0/myosin VI; 10043-52-4/Calcium Chloride; 56-40-6/Glycine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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