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This image shows the structures of Cap32/34 superposed onto CapZ (in green) over the Cα positions of the entire CP molecules.[1]

In molecular biology CapZ, also known as CAPZ; CAZ1 and CAPPA1, is a protein composed of alpha and beta subunits.[2] Its main function is to cap the barbed (plus) end of actin filaments in muscle cells. It is located in the Z band of the muscle sarcomere. This protein helps to stabilize the actin filaments protecting it from assembly and disassembly. The activity regulation of this protein can be done by other regulatory proteins that bind to the actin filaments blocking the CapZ, hence allowing assembly.[3] CapZ is also known to play a role in cell signaling, as it regulates PKC activity in cardiac cells.[4]


Experimentation on chicken muscles have indicated that there are certain proteins that inhibit CapZ from binding. This includes PIP2 and other phosphoplipids. These molecules bind to CapZ itself to prevent it from binding to actin. However, introduction of certain detergents (in this case Triton X 100) prevent the binding of these molecules to CapZ; in turn allowing it to bind to the microfilament.[5][6] Competition for actin binding sites can also regulate CapZ binding, as seen with filament elongation factors. These factors include ENA/VASP (enabled/vasodilator-stimulated phosphoprotein).[7] CapZ is not regulated by calcium or calmodulin, as seen with other capping proteins, such as Gelsolin.[8]

Cell movement[edit]

CapZ also plays a role in cell movement (cell crawling) by controlling the lengths of the microfilaments. When CapZ is inhibited by regulating factors, microfilament polymerization or depolymerization occurs allowing lamellipodia and filopodia to grow out or retract. This polymerization and depolymerization gives the cell the appearance of crawling. When CapZ binds, it halts both of these processes.[9]

Cardiac health[edit]

A modest reduction in cardiac CapZ protein protects hearts against acute ischemia-reperfusion injury.[10]


  1. ^ Eckert, C.; Goretzki, A.; Faberova, M.; Kollmar, M. (2012). "Conservation and divergence between cytoplasmic and muscle-specific actin capping proteins: Insights from the crystal structure of cytoplasmic Cap32/34 from Dictyostelium discoideum". BMC Structural Biology. 12: 12. doi:10.1186/1472-6807-12-12. PMC 3472329Freely accessible. PMID 22657106. 
  2. ^ Yamashita, Atsuko; Maeda, Kayo; Maéda, Yuichiro (2003-04-01). "Crystal structure of CapZ: structural basis for actin filament barbed end capping". The EMBO Journal. 22 (7): 1529–1538. doi:10.1093/emboj/cdg167. ISSN 0261-4189. PMC 152911Freely accessible. PMID 12660160. 
  3. ^ Lodish, Harvey; Berk, Arnold; Kaiser, Chris; Krieger, Monty; Bretscher, Antony; Ploegh, Hidde; Amon, Angelika; Scott, Matthew. Molecular Cell Biology (7th ed.). p. 783. ISBN 9781429234139. 
  4. ^ Yang, Fenghua; Aiello, David L.; Pyle, W. Glen (2008-02-01). "Cardiac myofilament regulation by protein phosphatase type 1alpha and CapZ". Biochemistry and Cell Biology = Biochimie Et Biologie Cellulaire. 86 (1): 70–78. doi:10.1139/o07-150. ISSN 1208-6002. PMID 18364747. 
  5. ^ "CapZ". Retrieved 2016-11-06. 
  6. ^ Heiss, Steven; Cooper, John (June 24, 1991). "Regulation of CapZ, an actin capping protein of chicken muscle, by anionic phospholipids". Biochemistry. 30. 
  7. ^ Edwards, Marc; Zwolak, Adam; Schafer, Dorothy A.; Sept, David; Dominguez, Roberto; Cooper, John A. (2014-10-01). "Capping protein regulators fine-tune actin assembly dynamics". Nature Reviews Molecular Cell Biology. 15 (10): 677–689. doi:10.1038/nrm3869. ISSN 1471-0072. PMC 4271544Freely accessible. PMID 25207437. 
  8. ^ Gremm, D.; Wegner, A. (2000-07-01). "Gelsolin as a calcium-regulated actin filament-capping protein". European Journal of Biochemistry. 267 (14): 4339–4345. doi:10.1046/j.1432-1327.2000.01463.x. ISSN 0014-2956. PMID 10880956. 
  9. ^ Hug, Christopher; Jay, Patrick Y.; Reddy, Indira; McNally, James G.; Bridgman, Paul C.; Elson, Elliot L.; Cooper, John A. (1995-05-19). "Capping protein levels influence actin assembly and cell motility in dictyostelium". Cell. 81 (4): 591–600. doi:10.1016/0092-8674(95)90080-2. 
  10. ^ Yang, Feng Hua; Pyle, WG (2 Dec 2011). "Reduced cardiac CapZ protein protects hearts against acute ischemia-reperfusion injury and enhances preconditioning". Journal of Molecular and Cellular Cardiology. 52 (3): 761–72. doi:10.1016/j.yjmcc.2011.11.013. PMID 22155006. 


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