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Adducin

 

Peters Lab Adducin 

A heterodimeric protein, associated with the membrane skeleton, which promotes the binding of spectrin to actin in a calcium/calmodulin dependent manner.  The protein is composed of two similar sub-units, a-adducin ( 103kd) and b-adducin (97kd) which together form higher order structures (dimers & tetramers) (Matsuoka et al, ).  Each sub-unit is composed of two distinct domains:- a globular, protease resistant head domain and a helical tail domain.  The head domain contains a sequence which is similar to the actin binding domain of the ABP-120, dystrophin, a-actinin group.  However as attempts to bind this domain to F-actin have failed, the significance of this is uncertain. The tail domain contains the putative calmodulin binding sites and the sites of phosphorylation by protein kinase A.  Protein kinase C sites are thought to be close to the junction of the head and tail domains.  A MARKS homologous domain is present at the C-terminus of  adducin that is thought to be responsible for actin binding. The dimers are thought to bind head to head and tail to tail in an parallel fashion, via the neck region which would be consistent with the reported bundling activity. Adducin apparently recruits spectrin to the barbed ends of actin filaments through the MARKS domain (Li et al, 1998) capping the filaments so that in the erythrocyte at least CapZ cannot bind the filaments (Kuhlman & Fowler, 1997).  Although this protein was first isolated from erythrocyte membrane it has since been found in other tissues such as kidney, brain and liver and in Drosophila a homolog is required for ring canal formation (Yue & Spradling, 1992).

Adducin and Hypertension

A spontaneous hypertensive rat strain has been identified and revealed later to be caused by a mutation in an adducin gene.  It seems that adducin may be connected to the disease as it has been found that adducin associates with the Na+-K+-ATPase (Ferrandi et al, 1999).

 

References:-

Ferrandi, M., Salardi, S., Tripodi, G., Barassi, P., Rivera, R., Manunta, P., Goldshleger, R., Ferrari, P., Bianchi, G. & Karlish, S. J. (1999) Evidence for an interaction between adducin and Na+-K+-ATPase: relation to genetic hypertension., Am.J.Physiol. 277, H1338-H1349.

Kuhlman, P. A. and V. M. Fowler (1997). "Purification and characterization of an a1b2 isoform of CapZ from human erythrocytes: Cytosolic location and inability to bind to Mg2+ ghosts suggest that erythrocytes actin filaments are capped by adducin." Biochemistry 36, 13461-13472.

Li, X., Y. Matsuoka, et al. (1998). "Adducin prefferentially recruits spectrin to the fast growing ends of actin filaments in a complex requiring the MARKS-related domain and a newly defined oligomerization domain." J.Biol.Chem. 273(30),  19329-19338.

Matsuoka, Y., X. Li, et al. (2000). "Adducin: Structure, function and regulation." Cell and Molecular Life Sciences 57, 884-895.

Yue, L., & Spradling, A.C. (1992). "hu-li tai shao, a gene required for ring canal formation during Drosophila oogenesis, encodes a homolog of adducin." Genes Dev. 6, 2443-2454.

 
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