This family consists of the highly related rubber elongation factor (REF), small rubber particle protein (SRPP) and stress-related protein (SRP) sequences. REF and SRPP are released from the rubber particle membrane into the cytosol during osmotic lysis of the sedimentable organelles (lutoids). The exact function of this family is unknown [1].

1: Characterization of polypeptides accumulated in the latex cytosol of rubber trees affected by the tapping panel dryness syndrome. Sookmark U, Pujade-Renaud V, Chrestin H, Lacote R, Naiyanetr C, Seguin M, Romruensukharom P, Narangajavana J; Plant Cell Physiol 2002;43:1323-1333. PMID:12461132