NPF is a natively unstructured but well-conserved region found in eukaryotic proteins of the Rabenosyn-5 type, wherein the sequence motif arginine-proline-phenylalanine followed by several glutamates and aspartates is repeated up to four times along the sequence. NPF lies between the two Rab-binding domains, for Rab-4 and Rab-5, at the C-terminal end of these proteins [1]. Rabosyn-5 (or rabenosyn) is also involved in cell-polarity determination in developing wing epithelia of Drosophila, when the NPF-motif may be implicated [2]. These NPF motifs create a region of strong positive surface potential which appear to bind Eps15 homology, EH or EF-hand, domains on proteins involved in vesicle trafficking [3].

1: Mapping of the basic amino-acid residues responsible for tubulation and cellular protrusion by the EFC/F-BAR domain of pacsin2/Syndapin II. Shimada A, Takano K, Shirouzu M, Hanawa-Suetsugu K, Terada T, Toyooka K, Umehara T, Yamamoto M, Yokoyama S, Suetsugu S; FEBS Lett. 2010;584:1111-1118. PMID:20188097

2: A novel function for the Rab5 effector Rabenosyn-5 in planar cell polarity. Mottola G, Classen AK, Gonzalez-Gaitan M, Eaton S, Zerial M; Development. 2010;137:2353-2364. PMID:20534670

3: Charge effects in the selection of NPF motifs by the EH domain of EHD1. Henry GD, Corrigan DJ, Dineen JV, Baleja JD; Biochemistry. 2010;49:3381-3392. PMID:20329706