Protein subunit

Source: Wikipedia, the free encyclopedia.
binding pocket
) of heterologous origin that also contributes to function.

In

polypeptide chain or single protein molecule that assembles (or "coassembles") with others to form a protein complex.[1][2][3]
Large assemblies of proteins such as
viruses often use a small number of types of protein subunits as building blocks.[4]

A subunit is often named with a Greek or Roman letter, and the numbers of this type of subunit in a protein is indicated by a subscript.[5] For example, ATP synthase has a type of subunit called α. Three of these are present in the ATP synthase molecule, leading to the designation α3. Larger groups of subunits can also be specified, like α3β3-hexamer and c-ring.[6]

Naturally occurring proteins that have a relatively small number of subunits are referred to as oligomeric.[7] For example, hemoglobin is a symmetrical arrangement of two identical α-globin subunits and two identical β-globin subunits.[3][8] Longer multimeric proteins such as microtubules and other cytoskeleton proteins may consist of very large numbers of subunits. For example, dynein is a multimeric protein complex involving two heavy chains (DHCs), two intermediate chains (ICs), two light-intermediate chains (LICs) and several light chains (LCs).[9]

The subunits of a protein complex may be identical, homologous or totally dissimilar and dedicated to disparate tasks.[1] In some protein assemblies, one subunit may be a "catalytic subunit" that enzymatically catalyzes a reaction, whereas a "regulatory subunit" will facilitate or inhibit the activity.[10] Although telomerase has telomerase reverse transcriptase as a catalytic subunit, regulation is accomplished by factors outside the protein.[11]

An enzyme composed of both regulatory and catalytic subunits when assembled is often referred to as a

polypeptide chain. A polypeptide chain has one gene
coding for it – meaning that a protein must have one gene for each unique subunit.

See also

References

  1. ^
    ISBN 978-1-305-68618-2
    . Retrieved 15 April 2022.
  2. ISBN 978-1-351-25807-4
    . Retrieved 15 April 2022.
  3. ^ a b Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter (2002). The Shape and Structure of Proteins. New York: Garland Science. Retrieved 15 April 2022.
  4. ISBN 978-81-7371-254-8
    . Retrieved 15 April 2022.
  5. ISBN 978-953-51-1617-2
    . Retrieved 15 April 2022.
  6. PMID 23432591
    .
  7. doi:10.1351/pac199668122287
    .Quote: Oligomer molecule: A molecule of intermediate relative molecular mass, the structure of which essentially comprises a small plurality of units derived, actually or conceptually, from molecules of lower relative molecular mass.
  8. ISBN 978-0-12-822383-3
    . Retrieved 15 April 2022.
  9. PMID 29899089
    .
  10. PMID 30258407
    .
  11. PMID 22381618
    .
  12. PMID 2174051
    .
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