A polyribosome (or polysome) is a complex of a mRNA molecule and two or more ribosomes that is formed during active translation.[1] Originally coined "ergosomes" in 1963 [2] they were further characterized by Jonathan Warner, Paul Knopf, and Alex Rich.[3] Polysomes can be directly visualized by electron microsopy because they form very high molecular weight particles.[1] Many ribosomes simultaneously read one mRNA progressing along the mRNA to synthesize the same protein. They may appear as linear polysomes or circular rosettes with microscopy but are mainly circular in vivo. This circularization is aided by the fact that mRNA is able to be twisted into a circular formation, creating a cycle of rapid ribosome recycling and utilization of ribosomes. The 5' 7-methylguanosine cap and 3' poly(A) tail present on eukaryotic mRNA aid in this process.[4]

Polyribosomes can be found in three forms: free, cytoskeletal bound, and membrane bound.


  1. ^ a b Michael M. Cox; Jennifer A. Doudna; Michael O'Donnell (July 2011). Molecular Biology: Principles and Practice. Macmillan Higher Education.  
  2. ^ Staehelin, T.; Brinton, C. C.; Wettstein, F. O.; Noll, H. (1963). "Structure and Function of E. Coli Ergosomes". Nature 199 (4896): 865–870.  
  3. ^ Warner JR, Knopf PM, Rich A (1963). "A multiple ribosomal structure in protein synthesis". Proc. Natl. Acad. Sci. U.S.A. 49: 122–129.   Summary
  4. ^ Harvey Lodish (1999). "4.5. Stepwise Formation of Proteins on Ribosomes". Molecular cell biology. New York: Scientific American Books.  

External links

  • Theoretical and experimental structure of polysome