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Profilin

updated 29/4/02A low molecular weight actin binding protein which seems to have been found in every eukaryotic species where it has been looked for.The protein was identified after the discovery of a non polymerised form of actin from Thyone sperm ! Tilney ". This comple# was found

to contain actin$ and a %&k'a protein and was named (profilamentous actin( ! Tilney$ " later abbreviated to (profilactin( ! Tilney$ %9)&b".

*owever$ although it is very likely that the %& k'a protein is profilin$ + do not believe that this has ever been shown. The name (profilin(

was coined by ,arlson from the previous term (profilactin(. The amino acid se-uence of the profilins are not very highly conserved

across the many phyla from those determined !proto oa$ mammalian$ yeast$ insect$ echinoderm$ plant and even a virus"$ yet despite this

the structure is conserved ! chutt et al $ %99 1 inson et al $ %99 13ederov et al $ %99413ederov et al $ %99)". ossibly connected with the

se-uence diversity$ the ubi-uity and abundance of profilins in eukaryotes is the fact that profilins are ma5or allergens. rofilin has an

unusual property in its ability to bind poly 6 proline$ and although the physiological significance of this accidental finding ! Tanaka 7

hibata$ %98 " is in itself very important$ this has provided an easy way to purify the protein ! :aiser et al $ %9891 ;anmey$ %99%". rofilin

binds to poly 6 proline as its actual function is to bind proline rich regions in a number of profilin binding proteins .

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lipase has been activated by phosphorylation ! >oldschmidt ,lermont et al $ %99% " bi and its low molecular weight ! about % kd"$ profilin

retains its ability to bind? actin$ poly proline$ and phosphoinositides. This ability to bind phosphoinositides is most intriguing and it has

even been suggested to be the primary role of the protein in cells$ since phosphoinositides provide a very important cell signalling

cascade$ transducing messages from outside to inside the cell.

The role of profilin in actin polymerization.

artly because of how it was first discovered and on its effects on the polymeri ation of pure actin$ profilin has been described primarily

as an actin monomer se-uestering protein. *owever$ it is now appreciated that the role of profilin is much more subtle than being merely

an actin se-uestering protein. +n some situations profilin encourages the polymeri ation of actin onto the barbed ends of actin filaments.

Intracellular localisation of profilin.

+n fibroblasts profilin has been found to be concentrated at the leading edge ! @u et al $ %992". rofilin is localised too to sites where + 2

is enriched in plant hair cells ! @raun et al $ %999"$ at the leading edge in the amoeba Acanthamoeba !@ubb et al $ %998"

The role of profilin in cytokinesis.

rofilin has been found to be necessary for complete cytokinesis in a number of organisms such as Schizosaccharomyces pombe

!@alasubramanian et al $ 994"$Saccharomyces cerevisiae !,hang et al, %99)"$ Dictyostelium discoidium !*augwit et al $ %994"

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The self-association of profilin?

ome reports suggest that profilin can self associate forming oligomers ! @abich et al $ %99&"

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The role of profilin in formin-nucleated actin cable assembly[ Edit ]

rofilin binds simultaneously to formin and actin monomers1 this interaction tethers multiple profilin actin comple#es near thegrowing end of actin filaments$ which promotes the processive addition of actin subunits %$ 2B. rofilin uses the energy from AThydrolysis generated during actin polymeri ation to facilitate actin assembly 2B. rofilin binds to cytoplasmic AT actin monomers

better than cytoplasmic A' actin monomers B.

rofilin has been suggested to generally increase the elongation rate of formin associated filaments by?

C ,ataly ing the e#change of A' for AT on actin monomers 4$ B.C @locking free monomers from elongating pointed ends 4B.C 6owering the critical concentration at the barbed end 2B.C romoting the association of > actin AT to the barbed end &B.

+mportantly however$ profilin also promotes disassembly of actin filaments by se-uestering monomeric > actin$ thereby blocking itsassociation with the barbed ends and promoting its disassembly from the pointed ends of actin filaments 4B. The combined actions of

profilin and A'3/cofilin synergi e to enhance turnover of actin filaments ) B.

References

https://sites.google.com/a/mechanobio.info/mbinfo_go_2013/modules/go-0070649/3_go-0070649http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID9214622http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8252614http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8252614http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8252614http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8647830http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID10409644http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID18835900http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID18835900http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID10409644http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8252614http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID10601251http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID10409644http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID9748225https://sites.google.com/a/mechanobio.info/mbinfo_go_2013/modules/go-0070649/3_go-0070649http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID9214622http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8252614http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8252614http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8647830http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID10409644http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID18835900http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID10409644http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID8252614http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID10601251http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID10409644http://www.mechanobio.info/modules/go-0070649/3_go-0070649#PMID9748225

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%. Datanabe .$ :aki uka A.$ aito F.$ =T*istory=@+nfo by =@+$

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