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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.

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

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

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

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.

Characteristic K01 mK01 mK02
Oligomerization Dimer Monomer Monomer
Number of Amino Acid 218 218 218
Excit./Emiss. maxima (nm) 548/561 548/559 551/565
Molar Extinction Coefficient (M-¹cm-¹) 73,700 (548 nm) 51,600 (548 nm) 63,800 (551 nm)
Fluorescence quantum yield 0.45 0.60 0.62
Brightness*¹ 33.2 31.0 39.6
pH sensitivity pKa<5.0 pKa<5.0 pKa=5.5
Cytotoxicity*² Not observed Not observed Not observed
Resistance to PFA fixation Not tested Not 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