This family includes Frag1, DRAM and Sfk1 proteins. Frag1 (FGF receptor activating protein 1) is a protein that is conserved from fungi to humans. There are four potential iso-prenylation sites throughout the peptide, viz CILW, CIIW and CIGL. Frag1 is a membrane-spanning protein that is ubiquitously expressed in adult tissues suggesting an important cellular function [1]. Dram is a family of proteins conserved from nematodes to humans with six hydrophobic transmembrane regions and an Endoplasmic Reticulum signal peptide. It is a lysosomal protein that induces macro-autophagy as an effector of p53-mediated death, where p53 is the tumour-suppressor gene that is frequently mutated in cancer. Expression of Dram is stress-induced [2]. This region is also part of a family of small plasma membrane proteins, referred to as Sfk1, that may act together with or upstream of Stt4p to generate normal levels of the essential phospholipid PI4P, thus allowing proper localisation of Stt4p to the actin cytoskeleton [3].

1: Human FRAG1 encodes a novel membrane-spanning protein that localizes to chromosome 11p15.5, a region of frequent loss of heterozygosity in cancer. Lorenzi MV, Castagnino P, Aaronson DC, Lieb DC, Lee CC, Keck CL, Popescu NC, Miki T; Genomics. 1999;62:59-66. PMID:10585768

2: DRAM, a p53-induced modulator of autophagy, is critical for apoptosis. Crighton D, Wilkinson S, O'Prey J, Syed N, Smith P, Harrison PR, Gasco M, Garrone O, Crook T, Ryan KM; Cell. 2006;126:121-134. PMID:16839881

3: Stt4 PI 4-kinase localizes to the plasma membrane and functions in the Pkc1-mediated MAP kinase cascade. Audhya A, Emr SD; Dev Cell. 2002;2:593-605. PMID:12015967