Kusabira Orange Fluorescent Protein

  • Bright orange fluorescence
  • High pH stability
  • Monomer/dimer

CoralHue® Kusabira-Orange (KO1), from the stony coral Fungia concinna (Kusabira-ishi in Japanese), absorbs light maximally at 548 nm and emits orange light at 561 nm. KO1 rapidly matures to form a fluorescent dimeric complex. KO1 can be used to mark cells or to report gene expression without problems stemming from protein aggregation.

CoralHue® monomeric Kusabira Orange (mKO1) maintains the brilliance and pH stability of the parent protein. mKO1 can be used to label proteins or subcellular structures or for FRET analysis.

CoralHue® mKO2 is a mutant of mKO1 that features rapid maturation. mKO2 can be used to label proteins or subcellular structures or for reporter assays.

Performance and Use

Kusabira-Orange are useful for labeling organelle.


Kusabira-Orange is easily expressed and detected in a wide range of organisms. It has been demonstrated in nucleoplasm, plasma membrane, endoplasmic reticulum and mitochondrial targeting signal models.

Kusabira-Orange is a useful protein for expression into various species.

Kusabira Orange 4

K01 TG pig – Provided by Dr. Nagashima,  Meiji University,  Cloning and Stem Cells. (2008) 10: 313-324.

mKO1 fused with Vasa protein expressed in Drosophila ovary (red). – Provided by Dr. Nakamura RIKEN 

Kusabira Orange 6

The olfactory bulb of zebrafish – Provided by Dr. Miyasaka and Dr. Yoshihara, Laboratory for Neurology of Synapse, BSI, RIKEN

Kusabira Orange 7

KO1 expressed in the epidermis of onion – Provided by Dr. Iida and Dr. Hoshino, the National Institute of Basic Biology (NIBB).


  1. Karasawa S, Araki T, Yamamoto-Hino M, Miyawaki A, A green-emitting fluorescent protein from Galaxeidae coral and its monomeric version for use in fluorescent labeling; J Biol Chem. 278, 34167-34171 (2003) PMID: 12819206
  2. Ebisawa T, Yamamura A, Kameda Y, Hayakawa K, Nagata K, Tanokura M. Crystallization and preliminary X-ray analysis of a monomeric mutant of Azami-Green (mAG), an Aequorea victoria green fluorescent protein-like green-emitting fluorescent protein from the stony coral Galaxea fascicularis. Acta Crystallogr Sect F Struct Biol Cryst Commun. 65(Pt 12):1292-5. (2009) PMID: 20054132

Fluorescent Properties

Kusabira-Orange1 excitation (8K)Kusabira-Orange1 emission (8K)
mKusabira-Orange1 excitation (8K)mKusabira-Orange1 emission (8K)
mKusabira-Orange2 excitation (4K)mKusabira-Orange2 emission (8K)

Note: The file is in a tab-delimited text format. It contains values of the wavelength (0.5nm spacing) and brightness (fluorescence intensity peak value normalized to 1). Use a spreadsheet program to create a spectrum that will help you in choosing the appropriate excitation filter, dichroic mirror and fluorescence filter.

Number of Amino Acid218218218
Excit./Emiss. maxima (nm)548/561548/559551/565
Molar Extinction Coefficient (M-¹cm-¹)73,700 (548 nm)51,600 (548 nm)63,800 (551 nm)
Fluorescence quantum yield0.450.600.62
pH sensitivitypKa<5.0pKa<5.0pKa=5.5
Cytotoxicity*²Not observedNot observedNot observed
Resistance to PFA fixationNot testedNot tested+++

*1Brightness: Molar Extinction Coefficient ×Fluorescence Quantum Yield / 1000

*2Toxicity when expressed in HeLa cells

Recommended Antibodies

CoralHue® KO1, mKO1 and mKO2 can be recognized using antibodies as shown below.

WB: Western blotting, IP: Immunoprecipitation, IC: Immunocytochemistry, IH: Immunohistochemistry