Lipid-binding proteins in plants

Abstract

Plant cells contain water-soluble proteins able to facilitate in vitro intermembrane transfer of phospholipids (phospholipid transfer proteins, PLTP) or to bind long-chain fatty acids (fatty acid binding proteins, FABP). PLTPs, purified to homogeneity from various plant organs (seeds or leaves) are, in major part, low molecular-mass proteins (9kDa), basic (pI around 9) and non-specific for phospholipids. FABPs, purified from seedlings, have also a low molecular mass (8.7 kDa), a high pI (8.4) and are non-specific for fatty acids. Interestingly, recent observations indicated that PLTPs are also able to bind fatty acids. Are PLTPs and FABPs the same protein? To try for an answer to this question, a comparison of the properties of both categories of proteins will be presented in this paper. Also, possible physiological functions of these proteins will be considered and hypotheses on their role in vivo will be discussed. In addition, new perspectives opened by the use of these proteins as tools for membrane studies will be presented.