Oleosin
Encyclopedia
Oleosins are structural proteins
found in vascular plant oil bodies
and found in plant cells. Oil bodies are not considered organelles because they have a single layer membrane and lack the pre-requisite double layer membrane in order to be considered an organelle. They are found in plant parts with high oil
content that undergo extreme desiccation as part of their maturation process, and help stabilize the bodies.
Oleosins comprise of three parts. The N-
and C-terminal domain
s are amphipathic, whereas the middle part is strongly hydrophobic. Models show oleosins having a hairpin
-like hydrophobic shape that is inserted inside the triacylglyceride
(TAG), while the hydrophilic parts are left outside oil bodies.
Oleosins have been found on oil bodies of seeds, tapetum
cells, and pollen
but not fruit
s. Instead of a stabilizer of oil bodies, oleosins are believe to be involved in water-uptaking of pollen on stigma.
in plants. If the protein is made as a fusion protein
with oleosin and a protease
recognition site is incorporated between them, the fusion protein will sit in the membrane of the oil body, which can be easily isolated by centrifugation
. The oil droplets can then be mixed with aqueous medium again, and oleosin cleaved from the protein of interest. Centrifugation will cause two phases to separate again, and the aqueous medium now contains the purified protein.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
found in vascular plant oil bodies
Oil body
An oil body is a lipid-containing structure found in plant cells. The term can refer to at least two distinct kinds of structures in different kinds of plants.-Oil bodies in liverworts:...
and found in plant cells. Oil bodies are not considered organelles because they have a single layer membrane and lack the pre-requisite double layer membrane in order to be considered an organelle. They are found in plant parts with high oil
Oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....
content that undergo extreme desiccation as part of their maturation process, and help stabilize the bodies.
Oleosins comprise of three parts. The N-
N-terminal end
The N-terminus refers to the start of a protein or polypeptide terminated by an amino acid with a free amine group . The convention for writing peptide sequences is to put the N-terminus on the left and write the sequence from N- to C-terminus...
and C-terminal domain
C-terminal end
The C-terminus is the end of an amino acid chain , terminated by a free carboxyl group . When the protein is translated from messenger RNA, it is created from N-terminus to C-terminus...
s are amphipathic, whereas the middle part is strongly hydrophobic. Models show oleosins having a hairpin
Hairpin
A hair pin or hairpin is a long device used to hold a person's hair in place.Hairpins made of metal, ivory, bronze, carved wood, etc. were used in ancient Assyria and Egypt for securing decorated hairstyles. Such hairpins suggest, as graves show, that many were luxury objects among the Egyptians...
-like hydrophobic shape that is inserted inside the triacylglyceride
Triglyceride
A triglyceride is an ester derived from glycerol and three fatty acids. There are many triglycerides, depending on the oil source, some are highly unsaturated, some less so....
(TAG), while the hydrophilic parts are left outside oil bodies.
Oleosins have been found on oil bodies of seeds, tapetum
Tapetum
Tapetum can refer to:* Tapetum * Tapetum lucidum* Tapetum of corpus callosum...
cells, and pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
but not fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
s. Instead of a stabilizer of oil bodies, oleosins are believe to be involved in water-uptaking of pollen on stigma.
Use in Purification of Recombinant Protein
Oleosins provide an easy way of purifying proteins which have been produced recombinantlyRecombinant DNA
Recombinant DNA molecules are DNA sequences that result from the use of laboratory methods to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in biological organisms...
in plants. If the protein is made as a fusion protein
Fusion protein
Fusion proteins or chimeric proteins are proteins created through the joining of two or more genes which originally coded for separate proteins. Translation of this fusion gene results in a single polypeptide with functional properties derived from each of the original proteins...
with oleosin and a protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
recognition site is incorporated between them, the fusion protein will sit in the membrane of the oil body, which can be easily isolated by centrifugation
Centrifugation
Centrifugation is a process that involves the use of the centrifugal force for the sedimentation of mixtures with a centrifuge, used in industry and in laboratory settings. More-dense components of the mixture migrate away from the axis of the centrifuge, while less-dense components of the mixture...
. The oil droplets can then be mixed with aqueous medium again, and oleosin cleaved from the protein of interest. Centrifugation will cause two phases to separate again, and the aqueous medium now contains the purified protein.