Rho-related GTPases from plants, otherwise known as ROPs, are involved in

cell polarity Cell polarity refers to spatial differences in shape, structure, and function within a cell. Almost all cell types exhibit some form of polarity, which enables them to carry out specialized functions. Classical examples of polarized cells are de ...

through the regulation of cytoskeleton components like actin and

microtubules Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...

. Unlike mammalian cells, plant cells do not contain heterotrimeric G proteins like

Cdc42 Cell division control protein 42 homolog (Cdc42 or CDC42) is a protein that in humans is encoded by the ''CDC42'' gene. Cdc42 is involved in regulation of the cell cycle. It was originally identified in ''S. cerevisiae'' (yeast) as a mediator of ...

, Rac, and Rho that are known to regulate cellular polarity. __TOC__

Structure and Function

ROP proteins are a type of monomeric G proteins found in plants belonging to the Rho family. ROP binding to GTP or GDP determines its activity due to conformational changes within its structure. Within the G-domain of the structure are the G-box motifs G1-5. These motifs are formed during protein folding and are composed of conserved sequences that are responsible for

nucleotide Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...

and

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

binding as well as

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

of GTP. Motifs G2 (switch I loop) and G3 (switch II loop) possess distinct conformations depending on GTP binding state. In addition, the G-domain contains a unique and conserved helical domain commonly found in Rho family proteins called αi. Specific locations within the 3D ROP protein structure, including the

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

13-20, 60-64, and 118-121, act as binding sites during protein activity. The serine residue at amino acid 74 has been shown to be a potential protein activity regulation site through phosphorylation.

References

Signal transduction EC 3.6.5 Plant proteins {{protein-stub