Cysteine-rich protein explained

Cysteine-rich proteins (CRP, cysteine-rich peptide or disulphide-rich peptide) are small proteins that contain a large number of cysteines. These cysteines either cross-link to form disulphide bonds, or bind metal ions by chelation, stabilising the protein's tertiary structure.[1] [2] [3] CRPs include a highly conserved secretion peptide signal at the N-terminus and a cysteine-rich region at the C-terminus.[4]

Structure

Disulphides

In an oxidising environment cysteines cross-link to form disulphide bonds. CRPs that form these typically have an even number of cysteines.[5]

Metal binding

Cysteines can coordinate one or more metal ions by forming a chelation complex around them.[6]

Functions in plants

CRPs are numerous in plants, with 756 CRP-encoding genes in the Arabidopsis thaliana genome.[7] Several CRPs bind known receptors,[8] but most CRP signaling mechanisms and protein interactions are uncharacterized. Characterized CRPs function as short-range intercellular signals during processes such as plant defense, bacterial symbiosis, stomatal patterning, fertilization, vegetative tissue development, and seed development.

Many CRPs function in plant defense. Defensins, a major class of CRP with an eight-cysteine motif forming four disulfide bridges,[9] are involved in pathogen response. Other putative antimicrobial CRPs include lipid transfer proteins, thionins, knottins, heveins, and snakins. Additionally, some CRPs have allergenic, ɑ-amylase inhibitory, or protease inhibitory functions that deter herbivores.

In plant reproduction, CRPs are involved in pollen tube growth and guidance[10] and early embryo patterning,[11] in addition to other functions. Among those involved in pollen tube attraction are the LUREs, a group of ovular pollen-tube attractants in Arabidopsis thaliana and Torenia fournieri[12] that preferentially attract conspecific pollen, and STIG1, a CRP expressed in the stigma of Solanum lycopersicum that interacts with the pollen-specific receptor PRK2. In early embryo development, CRPs such as ESF1 are necessary for suspensor development and normal seed morphology.

Notes and References

  1. Cheek S, Krishna SS, Grishin NV . Structural classification of small, disulfide-rich protein domains . Journal of Molecular Biology . 359 . 1 . 215–37 . May 2006 . 16618491 . 10.1016/j.jmb.2006.03.017 .
  2. Arolas JL, Aviles FX, Chang JY, Ventura S . Folding of small disulfide-rich proteins: clarifying the puzzle . Trends in Biochemical Sciences . 31 . 5 . 292–301 . May 2006 . 16600598 . 10.1016/j.tibs.2006.03.005 . 30709875 .
  3. Book: Metallothioneins and related chelators. 2009. Royal Society of Chemistry. Sigel, Astrid., Sigel, Helmut., Sigel, Roland K. O.. 978-1-84755-953-1. Cambridge. 429670531.
  4. Marshall E, Costa LM, Gutierrez-Marcos J . Cysteine-rich peptides (CRPs) mediate diverse aspects of cell-cell communication in plant reproduction and development . Journal of Experimental Botany . 62 . 5 . 1677–86 . March 2011 . 21317212 . 10.1093/jxb/err002 . free .
  5. Lavergne. Vincent. J. Taft. Ryan. F. Alewood. Paul. 2012-08-01. Cysteine-Rich Mini-Proteins in Human Biology. Current Topics in Medicinal Chemistry. 12. 14. 1514–1533. 10.2174/156802612802652411. 22827521 . 1568-0266.
  6. Maret. Wolfgang. 2008-05-01. Metallothionein redox biology in the cytoprotective and cytotoxic functions of zinc. Experimental Gerontology. Zinc and Ageing (ZINCAGE Project). en. 43. 5. 363–369. 10.1016/j.exger.2007.11.005. 18171607 . 19456564 . 0531-5565.
  7. Huang Q, Dresselhaus T, Gu H, Qu LJ . Active role of small peptides in Arabidopsis reproduction: Expression evidence . Journal of Integrative Plant Biology . 57 . 6 . 518–21 . June 2015 . 25828584 . 10.1111/jipb.12356 .
  8. Huang WJ, Liu HK, McCormick S, Tang WH . Tomato Pistil Factor STIG1 Promotes in Vivo Pollen Tube Growth by Binding to Phosphatidylinositol 3-Phosphate and the Extracellular Domain of the Pollen Receptor Kinase LePRK2 . The Plant Cell . 26 . 6 . 2505–2523 . June 2014 . 24938288 . 4114948 . 10.1105/tpc.114.123281 .
  9. Silverstein KA, Moskal WA, Wu HC, Underwood BA, Graham MA, Town CD, VandenBosch KA . Small cysteine-rich peptides resembling antimicrobial peptides have been under-predicted in plants . The Plant Journal . 51 . 2 . 262–80 . July 2007 . 17565583 . 10.1111/j.1365-313X.2007.03136.x . free .
  10. Zhong S, Liu M, Wang Z, Huang Q, Hou S, Xu YC, Ge Z, Song Z, Huang J, Qiu X, Shi Y, Xiao J, Liu P, Guo YL, Dong J, Dresselhaus T, Gu H, Qu LJ . 6 . Arabidopsis . Science . 364 . 6443 . eaau9564 . May 2019 . 31147494 . 10.1126/science.aau9564 . 7184628 .
  11. Costa LM, Marshall E, Tesfaye M, Silverstein KA, Mori M, Umetsu Y, Otterbach SL, Papareddy R, Dickinson HG, Boutiller K, VandenBosch KA, Ohki S, Gutierrez-Marcos JF . 6 . Central cell-derived peptides regulate early embryo patterning in flowering plants . Science . 344 . 6180 . 168–72 . April 2014 . 24723605 . 10.1126/science.1243005 . 2014Sci...344..168C . 3234638 .
  12. Kanaoka MM, Higashiyama T . Peptide signaling in pollen tube guidance . Current Opinion in Plant Biology . 28 . 127–36 . December 2015 . 26580200 . 10.1016/j.pbi.2015.10.006 . free .

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