IQ motif

Attachment of two light chains to the heavy chain of a myosin (from the sphincter muscle of Argopecten irradians , a scallop shell like the scallop ).
The (essential) light chain on the left binds to the regulatory region containing an IQ motif in the transverse section of the heavy chain (unfortunately also shown here in red, a Ca ion in green ).

The IQ motif is a widespread sequence motif in the amino acid sequence of various proteins , especially those that bind calmodulin . It is contained in a basic unit about two dozen amino acids long, the conserved motif of which usually corresponds in the consensus sequence

-IQxxxRxxxxR-

where I stands for isoleucine and Q for glutamine , R for arginine .

The three-dimensional amino acid chain of the IQ domain , unfolded into an amphipathic α-helix with seven turns , presents as a structural motif a binding domain for light chains, including the regulatory of un- / conventional myosins as well as calmodulin (CaM) and CaM-like.

Proteins that contain one or (often in copies) several IQ domains can be caused to change their conformation by adding appropriate ligands as a light chain - such as CaM or other regulating proteins - and thus be functionally influenced. For example, the in / activity of various functional proteins , such as motor proteins or others of the cytoskeleton , can be regulated in a coordinated manner by unbound / bound ligands - in the case of CaM also depending on the intracellular Ca ²⁺ level as a signal .

literature

Bruce Alberts , Alexander Johnson, Peter Walter, Julian Lewis, Martin Raff, Keith Roberts: Molecular Biology of the Cell . 5th edition, Taylor & Francis 2007, ISBN 978-0815341062 .
Jeremy M. Berg, John L. Tymoczko, Lubert Stryer : Biochemistry. 6 edition, Spektrum Akademischer Verlag, Heidelberg 2007, ISBN 978-3-8274-1800-5 .

Individual evidence

↑ ^a ^b A. Houdusse, C. Cohen: Structure of the regulatory domain of scallop myosin at 2 A resolution: implications for regulation . In: Structure . Volume 4, No. 1, January 1996, pp. 21-32. doi : 10.1016 / S0969-2126 (96) 00006-8 . PMID 8805510 .
^ A. Rhoads, F. Friedberg: Sequence motifs for calmodulin recognition . In: FASEB Journal . Volume 11, No. 5, April 1997, pp. 331-340. PMID 9141499 .
↑ M. Bähler, A. Rhoads: Calmodulin signaling via the IQ motif . In: FEBS Letters . 513, No. 1, February 2002, pp. 107-113. PMID 11911888 .

[pmid8805510-1] A. Houdusse, C. Cohen: Structure of the regulatory domain of scallop myosin at 2 A resolution: implications for regulation . In: Structure . Volume 4, No. 1, January 1996, pp. 21-32. doi : 10.1016 / S0969-2126 (96) 00006-8 . PMID 8805510 .

[pmid9141499-2] A. Rhoads, F. Friedberg: Sequence motifs for calmodulin recognition . In: FASEB Journal . Volume 11, No. 5, April 1997, pp. 331-340. PMID 9141499 .

[pmid11911888-3] M. Bähler, A. Rhoads: Calmodulin signaling via the IQ motif . In: FEBS Letters . 513, No. 1, February 2002, pp. 107-113. PMID 11911888 .