WordNet

slight or limited; especially in degree or intensity or scope; "a series of death struggles with small time in between"
a garment size for a small person
the slender part of the back
limited or below average in number or quantity or magnitude or extent; "a little dining room"; "a little house"; "a small car"; "a little (or small) group" (同)little
have fine or very small constituent particles; "a small misty rain"
on a small scale; "think small"

PrepTutorEJDIC

(大きさが)『小さい』,小形の;(量が)『少ない』,わずかな / 『取るに足りない』,ささいな(trivial) / 《名詞の前にのみ用いて》(仕事・活動などが)『小規模の』,ささやかな / 心が狭い,利己的な / (音・声が)弱い,小さい / (文字が)小型の,小文字の / 《the~》小さいもの;(…の)細い部分《+『of』+『名』》 / 《複数形で》《英》(衣類・ハンカチなどの)小物,小間物 / 小さく,細かく / (声などが)低く,弱く / 小規模に,こぢんまりと

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/03/31 12:30:31」(JST)

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Small GTPases (EC 3.6.5.2) are a family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). They are a type of G-proteins found in the cytosol that are homologous to the alpha subunit of heterotrimeric G-proteins, but unlike the alpha subunit of G proteins, a small GTPase can function independently as a hydrolase enzyme to bind to and hydrolyze a guanosine triphosphate (GTP) to form guanosine diphosphate (GDP). The most well-known members are the Ras GTPases and hence they are sometimes called Ras superfamily GTPases.

A typical G-protein is active when bound to GTP and inactive when bound to GDP (i.e. when the GTP is hydrolyzed to GDP). The GDP can be then replaced by free GTP. Therefore, a G-protein can be switched on and off. GTP hydrolysis is accelerated by GTPase activating proteins (GAPs), while GTP exchange is catalyzed by Guanine nucleotide exchange factors (GEFs). Activation of a GEF typically activates its cognate G-protein, while activation of a GAP results in inactivation of the cognate G-protein. Guanosine nucleotide dissociation inhibitors (GDI) maintain small GTP-ases in the inactive state.

Small GTPases regulate a wide variety of processes in the^[which?] cell, including growth, cellular differentiation, cell movement and lipid vesicle transport.

The Ras superfamily

There are more than a hundred proteins in the Ras superfamily.^[1] Based on structure, sequence and function, the Ras superfamily is divided into five main families, (Ras, Rho, Ran, Rab and Arf GTPases).^[2] The Ras family itself is further divided into 6 subfamilies: Ras, Ral, Rit, Rap, Rheb, and Rad. Miro is a recent contributor to the superfamily.

Each subfamily shares the common core G domain, which provides essential GTPase and nucleotide exchange activity.

The surrounding sequence helps determine the functional specificity of the small GTPase, for example the 'Insert Loop', common to the Rho subfamily, specifically contributes to binding to effector proteins such as IQGAP and WASP.

The Ras family is generally responsible for cell proliferation, Rho for cell morphology, Ran for nuclear transport and Rab and Arf for vesicle transport.^[3]

References

^ Wennerberg K, Rossman KL, Der CJ (March 2005). "The Ras superfamily at a glance". J. Cell. Sci. 118 (Pt 5): 843–6. doi:10.1242/jcs.01660. PMID 15731001.
^ Goitre, L; Trapani, E; Trabalzini, L; Retta, SF (26 December 2013). "The Ras superfamily of small GTPases: the unlocked secrets." 1120. pp. 1–18. doi:10.1007/978-1-62703-791-4_1. PMID 24470015. Retrieved 2 January 2015.
^ Munemitsu S, Innis M, Clark R, McCormick F, Ullrich A, Polakis P. (1990). "Molecular cloning and expression of a G25K cDNA, the human homolog of the yeast cell cycle gene CDC42". Mol Cell Biol 10 (11): 5977–82. ISSN 0270-7306. PMC 361395. PMID 2122236.

External links

Small GTPases at the US National Library of Medicine Medical Subject Headings (MeSH)

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English Journal

Lovastatin-Mediated Changes in Human Tendon Cells.

Kuzma-Kuzniarska M1, Cornell HR1, Moneke MC1, Carr AJ1, Hulley PA1.
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PMID 25846724

Mitochondria to nucleus signaling and the role of ceramide in its integration into the suite of cell quality control processes during aging.

Jazwinski SM1.
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Mitochondria to nucleus signaling has been the most extensively studied mode of inter-organelle communication. The first signaling pathway in this category of information transfer to be discovered was the retrograde response, with its own set of signal transduction proteins. The finding that this pa
PMID 25555678

Calcium is an organizer of cell polarity in plants.

Himschoot E1, Beeckman T2, Friml J3, Vanneste S4.
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Cell polarity is a fundamental property of pro- and eukaryotic cells. It is necessary for coordination of cell division, cell morphogenesis and signaling processes. How polarity is generated and maintained is a complex issue governed by interconnected feed-back regulations between small GTPase signa
PMID 25725133

Japanese Journal

活性硫黄種によるレドックス恒常性維持機構に基づいた新規心不全治療戦略の構築

西田基宏,外山喬士,熊谷嘉人,沼賀(冨田) 拓郎
YAKUGAKU ZASSHI 134(12), 1239-1243, 2014
… The switching mechanism of NO-mediated signaling includes formation of endogenous NO-derived electrophilic byproducts such as 8-nitroguanosine 3′,5′-cyclic monophosphate (8-nitro-cGMP), which selectively targets an oncogenic small GTPase H-Ras at Cys-184, leading to cardiac cell senescence via covalent modification (S-guanylation) and activation of H-Ras. …
NAID 130004712987

RhoJ defines angiogenic endothelial cell motility by integrating VEGF and Sema3E signals

Uemura Akiyoshi,Fukushima Yoko,Nishiyama Koichi,Ogura Yuichiro,Nishikawa Shin-Ichi
Microvascular Reviews and Communications 7(1), 37-37, 2014
… Here, we show that the small GTPase RhoJ is an EC-intrinsic integrator of VEGF and Sema3E signals. …
NAID 130004678475

Epigallocatechin gallate suppresses LPS endocytosis and nitric oxide productionby reducing Rab5-caveolin-1 interaction

HAGIWARA Makoto,MATSUSHITA Kenji
Biomedical Research 35(2), 145-151, 2014
… We also investigated themechanism with focus on the effect of EGCG on interaction between small GTPase Rab5 and caveolin-1. …
NAID 130004470860

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