The UNC-119 family of proteins is ubiquitous in animals. The expression of UNC-119 is prominent in neural tissues including photoreceptor cells. Homologues of UNC-119 are also found in ciliated (or flagellated) single-celled organisms; however, the cellular distribution of this protein in protists is unknown. We cloned and characterized a homologue of unc-119 from the ameboflagellate Naegleria gruberi (Ngunc-119) and identified the cellular distribution of the protein. The Ngunc-119 open reading frame contained 570 nucleotides encoding a protein of 189 amino acids with a predicted molecular weight of 22.1 kDa, which is similar to that of Paramecium UNC-119 and Trypanosoma UNC-119. These three proteins are 46-48% identical in their amino acid sequences. The smaller NgUNC-119 corresponds to the conserved C-terminal 3/4 of the UNC-119 from multi-cellular organisms. The amino acid sequence of NgUNC-119 is 43-50% identical to that of the conserved C-terminal regions. NgUNC-119 was not found in growing amoebae but accumulated rapidly after the initiation of differentiation into flagellates. Indirect immunofluorescence staining of differentiating N. gruberi showed that NgUNC-119 begins to concentrate at a spot near the nucleus of differentiating cells and then elongates into a filamentous structure. Purification and indirect immunofluorescence staining of the Naegleria flagellar rootlet suggested that NgUNC-119 is a component of the flagellar rootlet.
Bibliographical noteFunding Information:
The authors greatly appreciate Dr. C. Walsh (University of Pittsburgh) for suggestions on this manuscript. This work was supported by the Korea Research Foundation Grant funded by Korea Government (MOEHRD, Basic Research Promotion Fund) (KRF-2005-070-C00089) and a grant from Yonsei University (2002-0163) to J. Lee. S. Kang was also supported by 2nd Brain Korea 21 Research Program.
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