Jumat, 24 Juni 2011

Actin Filaments

Contractile activity in muscle cells results primarily from an interaction between two proteins: actin and myosin. Actin is present in muscle as a thin (5–7 nm in diameter) filament composed of globular subunits organized into a double-stranded helix (Figure 2–36). Structural and biochemical studies reveal that there are several types of actin and that this protein is present in all cells.

Figure 2-36
The cytosolic actin filament. Actin dimers are added to the plus (+) end and removed at the minus (–) end, dynamically lengthening or shortening the filament, as required by the cell. (Redrawn and reproduced, with permission, from Junqueira LC, Carneiro J: Biologia Celular e Molecular, 6th ed. Editora Guanabara, 1997.)












Within cells, microfilaments can be organized in many forms.
1. In skeletal muscle, they assume a paracrystalline array integrated with thick (16-nm) myosin filaments.
2. In most cells, actin filaments form a thin sheath just beneath the plasmalemma, called the cell cortex. These filaments appear to be associated with membrane activities such as endocytosis, exocytosis, and cell migratory activity.
3. Actin filaments are intimately associated with several cytoplasmic organelles, vesicles, and granules. The filaments are believed to play a role in moving and shifting cytoplasmic components (cytoplasmic streaming).
4. Actin filaments are associated with myosin and form a "purse-string" ring of filaments whose constriction results in the cleavage of mitotic cells.
5. In most cells, actin filaments are found scattered in what appears to be an unorganized fashion within the cytoplasm (Figure 2–31).
Although actin filaments in muscle cells are structurally stable, in nonmuscle cells they readily dissociate and reassemble. Actin filament polymerization appears to be under the direct control of minute changes in Ca2+ and cyclic AMP levels. A large number of actin-binding proteins have been demonstrated in a wide variety of cells, and much current research is focused on how these proteins regulate the state of polymerization and lateral aggregation of actin filaments. Their importance can be deduced from the fact that only about half the cell's actin is in the form of filaments.
Presumably, most actin filament-related activities depend upon the interaction of myosin with actin. (The structure and activity of the thick myosin filaments are described in the section on muscle tissues.)

References
Afzelius BA, Eliasson R: Flagellar mutants in man: on the heterogeneity of the immotile-cilia syndrome. J Ultrastruct Res 1979;69:43. [PMID: 501788]
Aridor M, Balch WE: Integration of endoplasmic reticulum signaling in health and disease. Nat Med 1999;5:745. [PMID: 10395318]
Barrit GJ: Communication Within Animal Cells. Oxford University Press, 1992.
Becker WM et al: The World of the Cell, 4th ed. Benjamin/Cummings, 2000.
Bretscher MS: The molecules of the cell membrane. Sci Am 1985;253:100. [PMID: 2416050]
Brinkley BR: Microtubule organizing centers. Annu Rev Cell Biol 1985;1:145. [PMID: 3916316]
Brown MS et al: Recycling receptors: the round-trip itinerary of migrant membrane proteins. Cell 1983;32:663. [PMID: 6299572]
Cooper GM: The Cell: A Molecular Approach. ASM Press/Sinauer Associates, Inc., 1997.
DeDuve C: A Guided Tour of the Living Cell. Freeman, 1984.
DeDuve C: Microbodies in the living cell. Sci Am 1983;248:74.
Dustin P: Microtubules, 2nd ed. Springer-Verlag, 1984.
Farquhar MG: Progress in unraveling pathways of Golgi traffic. Annu Rev Cell Biol 1985;1:447. [PMID: 3916320]
Fawcett D: The Cell, 2nd ed. Saunders, 1981.
KrstĂ­c RV: Ultrastructure of the Mammalian Cell. Springer-Verlag, 1979.
Mitchison TJ, Cramer LP: Actin-based cell motility and cell locomotion. Cell 1996;84:371. [PMID: 8608590]
Osborn M, Weber K: Intermediate filaments: cell-type-specific markers in differentiation and pathology. Cell 1982;31:303. [PMID: 6891619]
Pfeffer SR, Rothman JE: Biosynthetic protein transport and sorting in the endoplasmic reticulum. Annu Rev Biochem 1987;56:829. [PMID: 3304148]
Rothman J: The compartmental organization of the Golgi apparatus. Sci Am 1985;253:74. [PMID: 3929377]
Simons K, Ikonen E: How cells handle cholesterol. Science 2000;290:1721. [PMID: 11099405]
Tzagoloff A: Mitochondria. Plenum, 1982.
Weber K, Osborn M: The molecules of the cell matrix. Sci Am 1985;253:110. [PMID: 4071030]

 

6 comments:

Medical Health Information Resources

Thank you for sharing with us, I think this website really stands out

beauty

That makes complete sense!It sounds like a great book. Thanks for sharing.

sheen

Hey, just wanted to say that this was a very well written post and I enjoyed reading it.

It's great to see someone sharing interesting information on the internet....

arman

I have studied your site fully and I realized that, it is the most beneficial for us. I want to take more information through this site.

UI UX Designers Delhi

Amazing blog and very interesting stuff you got here! I definitely learned a lot from reading through some of your earlier posts as well and decided to drop a comment on this one!

Lea Paige Matteo

Chemicals used in industries gives me Leukemia Cancer and it's all started when I wanted to get off my job to get another job that when I got diagnose, at that very point I was so scared to die because it has infected my blood cells also I was prescribed drugs like Cyclophosphamide,Busulfan,Bosutinib,Cytarabine, Cytosar-U (Cytarabine),Dasatinib in all that was just to keep me waiting for my dying day. I got inspired by what I read from a lady called Tara Omar on blog spot on how Dr Itua cure her HIV/Aids then they were lettered below that says he can cure Cancer so I pick his contact on the testimony she wrote then I emailed Dr Itua hopefully he replied swiftly to my mail then I purchased his Herbal medicine also it was shipped to me here in Texas, I went to pick it at post office so he instructs me on how the treatment will take me three weeks to cure my Leukemia Disease, Joyfully I was cured by this Dr Itua Herbal Medicine.
I will advise you too to give a try to Dr Itua Herbal Medicine with the following diseases that he can help you cure forever___Diabetes, Herpes,HIV/Aids, Bladder Cancer, Breast Cancer, Parkinson's disease,Schizophrenia,Lung Cancer,Breast Cancer,Colo-Rectal Cancer,Blood Cancer,Prostate Cancer,siva.Fatal Familial Insomnia Factor V Leiden Mutation ,Epilepsy Dupuytren's disease,Desmoplastic small-round-cell tumor Diabetes ,Coeliac disease,Creutzfeldt–Jakob disease,Cerebral Amyloid Angiopathy, Ataxia,Arthritis,Amyotrophic Lateral Scoliosis,Fibromyalgia,Fluoroquinolone Toxicity
Syndrome Fibrodysplasia Ossificans ProgresSclerosis,Seizures,Alzheimer's disease,Adrenocortical carcinoma.Asthma,Allergic diseases.Copd,Glaucoma., Cataracts,Macular degeneration,Cardiovascular disease,Lung disease.Enlarged prostate,Osteoporosis.Alzheimer's disease,
Dementia.Vaginal Cancer, Kidney Cancer, Lung Cancer, Skin Cancer, Uterine Cancer, Prostate Cancer, Colo_Rectal Cancer, Leukemia Cancer, Hepatitis, Brain Tumors, Tach Disease,Love Spell, Infertility, Hpv. GoodLuck,XoXo****
Dr Itua Contact Information:::
Email (drituaherbalcenter@gmail.com)
WhatsApp-(+2348149277967)  

Posting Komentar

Posting Lebih Baru Posting Lama Beranda
Your 1:1 Traffic Exchange

 

Chat Box


Top Commentators

Give Me +1

Admin

Foto Saya
I created this blog just to support the activities of my learning about histology and others

Followers

Rank

 
Copyright © 2011 De Histology

Templates by Poncol Gate | CSS3 by David Walsh | Powered by {N}Code & Blogger