actin

1 of 2

noun

ac·​tin ˈak-tən How to pronounce actin (audio)
: a cellular protein found especially in microfilaments (such as those comprising myofibrils) and active in muscular contraction, cellular movement, and maintenance of cell shape

actin-

2 of 2

combining form

variants or actini- or actino-
1
: having a radiate form
actinolite
2
: actinic radiation (such as X-rays)
actinometer

Examples of actin in a Sentence

Recent Examples on the Web
Noun
Rome proposes that vaults might be ferrying the blueprint for actin to the construction sites. Betsy Hanson, Discover Magazine, 11 Nov. 2019 One place where vaults seem to clump together is where the cell is building long fibers of the protein actin that make up part of the cell’s internal skeleton. Betsy Hanson, Discover Magazine, 11 Nov. 2019 Structural basis of actin sequestration by thymosin-beta4: implications for WH2 proteins. The Salt Lake Tribune, 16 Aug. 2023 The cells produce specific proteins—actin and myosin—that cause muscles to contract and relax like rubber bands at different speeds. Lauren J. Young, Scientific American, 2 July 2023 Her team had not only isolated and cultivated the organism for the first time but shown that its flailing filaments were made of actin, the protein that forms a skeletal scaffold in almost all complex cells, or eukaryotes. Joshua Sokol, Quanta Magazine, 11 Apr. 2023 By amassing actin at their point of entry, Neisseria actually stimulates the cell to produce a barricade that prevents them from breaking through. Ed Yong, Discover Magazine, 25 Aug. 2010 Other microorganisms travel using amoeboid movement, driven by flexing of their cellular skeletons, built from the protein actin. Tom Siegfried, Smithsonian, 26 Sep. 2019 Filaments of the protein actin, for example, could have stabilized contacts between the hosts and symbionts and improved the coupling of their metabolisms. Quanta Magazine, 9 Apr. 2019

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'actin.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

Noun

probably from act entry 2 or act(ivate) + -in entry 1

Combining form

borrowed from Greek aktino-, from aktīn-, aktís "ray, beam, spoke of a wheel"

Note: The Greek word has traditionally been linked with Sanskrit aktú-, conjectured to mean "twilight," and with Germanic *uŋhtwōn- "last part of the night, dawn," whence Old English ūhte "twilight, daybreak," Old High German uohta "dawn," Old Norse ōtta "last part of the night," Gothic uhtwo "dawn," from Indo-European *n̥kwt-u-n-, a zero-grade derivative of *nokwt-/*nekwt- "night" (see night entry 1). Robert Beekes (Etymological Dictionary of Greek, Leiden, 2009) rejects this connection on the grounds that aktís "shows no trace of a labiovelar." In reference to actinic radiation, the formative actino- was probably first used by John herschel in actinometer (1833).

First Known Use

Noun

1942, in the meaning defined above

Time Traveler
The first known use of actin was in 1942

Dictionary Entries Near actin

Cite this Entry

“Actin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/actin. Accessed 15 Jul. 2024.

Kids Definition

actin

noun
ac·​tin ˈak-tən How to pronounce actin (audio)
: a protein of muscle that with myosin is active in muscular contraction

Medical Definition

actin

noun
ac·​tin ˈak-tən How to pronounce actin (audio)
: a protein found especially in microfilaments (as those comprising myofibrils) and active in muscular contraction, cellular movement, and maintenance of cell shape see f-actin, g-actin

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