Macromolecular assembly

Source: Wikipedia, the free encyclopedia.
Thomas Steitz. Of the 31 component proteins, 27 are shown (blue), along with its 2 RNA strands (orange/yellow).[1] Scale: assembly is approx. 24 nm across.[2]

The term macromolecular assembly (MA) refers to massive chemical structures such as

actin filaments and the flagellar motor, image). The process by which MAs are formed has been termed molecular self-assembly
, a term especially applied in non-biologic contexts. A wide variety of physical/biophysical, chemical/biochemical, and computational methods exist for the study of MA; given the scale (molecular dimensions) of MAs, efforts to elaborate their composition and structure and discern mechanisms underlying their functions are at the forefront of modern structure science.

elongation and other factors involved in light blue, the growing polypeptide chain as a black thread growing vertically from the curve of the mRNA. At end of the animation, the polypeptide produced is extruded through a light blue SecY pore[3] into the gray interior of the ER
.

Biomolecular complex

3D printed model of the structure of a bacterial flagellum "motor" and partial rod structure of a Salmonella species. Bottom to top: dark blue, repeating FliM and FliN, motor/switch proteins; red, FliG motor/switch proteins; yellow, FliF transmembrane coupling proteins; light blue, L and P ring proteins; and (at top), dark blue, the cap, hook-filament junction, hook, and rod proteins.[4]

A biomolecular complex, also called a biomacromolecular complex, is any biological complex made of more than one biopolymer (protein, RNA, DNA, [5] carbohydrate) or large non-polymeric biomolecules (lipid). The interactions between these biomolecules are non-covalent. [6] Examples:

The biomacromolecular complexes are studied structurally by

cryo-electron microscopy and successive single particle analysis, and electron tomography
. [9] The atomic structure models obtained by X-ray crystallography and biomolecular NMR spectroscopy can be docked into the much larger structures of biomolecular complexes obtained by lower resolution techniques like electron microscopy, electron tomography, and small-angle X-ray scattering. [10]

Complexes of macromolecules occur ubiquitously in nature, where they are involved in the construction of viruses and all living cells. In addition, they play fundamental roles in all basic life processes (

intermolecular interactions).[citation needed
]

MA scales and examples

The images above give an indication of the compositions and scale (dimensions) associated with MAs, though these just begin to touch on the complexity of the structures; in principle, each living cell is composed of MAs, but is itself an MA as well. In the examples and other such complexes and assemblies, MAs are each often millions of

protein crystallography and related methods, or studied by other physical methods (e.g., spectroscopy, microscopy).[citation needed
]

hydrophobic lipid tails; black and white spheres represent PL polar regions (v.i.). Bilayer/liposome dimensions (obscured in graphic): hydrophobic and polar regions, each ~30 Å (3.0 nm) "thick"—the polar from ~15 Å (1.5 nm) on each side.[11][12][13][non-primary source needed][14]
A graphical representation of the structure of a viral MA, cowpea mosaic virus, with 30 copies of each of its coat proteins, the small coat protein (S, yellow) and the large coat protein (L, green), which, along with 2 molecules of positive-sense RNA (RNA-1 and RNA-2, not visible) constitute the virion. The assembly is highly symmetric, and is ~280 Å (28 nm) across at its widest point.[verification needed][citation needed]

Biomembranes are also generally considered MAs, though the requirement for structural and spatial definition is modified to accommodate the inherent molecular dynamics of membrane lipids, and of proteins within lipid bilayers.[15]

Virus assembly

During assembly of the bacteriophage (phage) T4 virion, the morphogenetic proteins encoded by the phage genes interact with each other in a characteristic sequence. Maintaining an appropriate balance in the amounts of each of these proteins produced during viral infection appears to be critical for normal phage T4 morphogenesis.[16] Phage T4 encoded proteins that determine virion structure include major structural components, minor structural components and non-structural proteins that catalyze specific steps in the morphogenesis sequence[17]

Research into MAs

The study of MA structure and function is challenging, in particular because of their megadalton size, but also because of their complex compositions and varying dynamic natures. Most have had standard chemical and biochemical methods applied (methods of

Ada E. Yonath.[18]

Non-biologic counterparts

Finally, biology is not the sole domain of MAs. The fields of supramolecular chemistry and nanotechnology each have areas that have developed to elaborate and extend the principles first demonstrated in biologic MAs. Of particular interest in these areas has been elaborating the fundamental processes of molecular machines, and extending known machine designs to new types and processes.[citation needed]

See also

References

  1. PMID 10937989
    .
  2. ^ McClure W. "50S Ribosome Subunit". Archived from the original on 2005-11-24. Retrieved 2019-10-09.
  3. PMID 16212506
    .
  4. ^ Legend, cover art, J. Bacteriol., October 2006.[full citation needed]
  5. PMID 15980485
    .
  6. PMID 22577819
    .
  7. ^ Dutta S, Berman HM (March 2005). "Large macromolecular complexes in the Protein Data Bank: a status report". Structure. 13 (3): 381–388.
    PMID 15766539
    .
  8. PMID 15193311
    .
  9. S2CID 20148856
    .
  10. ^ "Structure of Fluid Lipid Bilayers". Blanco.biomol.uci.edu. 2009-11-10. Retrieved 2019-10-09.
  11. ^ Experimental system, dioleoylphosphatidylcholine bilayers. The hydrophobic hydrocarbon region of the lipid is ~30 Å (3.0 nm) as determined by a combination of neutron and X-ray scattering methods; likewise, the polar/interface region (glyceryl, phosphate, and headgroup moieties, with their combined hydration) is ~15 Å (1.5 nm) on each side, for a total thickness about equal to the hydrocarbon region. See S.H. White references, preceding and following.
  12. PMID 1547331
    .
  13. ^ Hydrocarbon dimensions vary with temperature, mechanical stress, PL structure and coformulants, etc. by single- to low double-digit percentages of these values.[citation needed]
  14. PMID 30877332
    .
  15. PMID 4907266
    .
  16. PMID 4878023
    .
  17. ^ "The Nobel Prize in Chemistry 2009". The Nobel Prize. Nobel Prize Outreach AB 2021. Retrieved 10 May 2021.

Further reading

General reviews

Reviews on particular MAs

Primary sources

Other sources

External links

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