Both frameshift mutations and several single nucleotide polymorphisms (SNPs) have been found correlated to a variety of lung conditions.
[11] These are found embedded into membranes and other lipid structures, SP-B is a highly hydrophobic, avoiding contact with water.
Synthesized in the endoplasmic reticulum of type II pneumocytes, proSP-B weighs approximately 40 kDa and is cut down to the size of mature SP-B in the golgi apparatus through a process called post-translational modification.
The lipid shown to be most needed on this surface (Dipalmitoylphosphatidylcholine) does not easily move to the gas/fluid interface, but SP-B helps ease and speed up this process.
[5] Effectively, SP-B cuts and pastes pieces of the lipid bilayers to form the three dimensional structure of the tubular myelin.
This structure is the support and lipid source for the gas/fluid interface, where surface tension is a critical factor in lung function.
Beyond arranging lipids in a way that reduces surface tension, SP-B actually directly interferes with attractive forces between water molecules.
Lamellar bodies are groups of lipids and protein that are structurally similar to tubular myelin, but are found inside instead of outside the type II pneumocytes.
Similarly to its function in organizing tubular myelin, SP-B arranges lipids into the lamellar body structure.
Surfactant is a mixture of lipids and proteins that coats the inside of alveoli and is essential for life due to its key role in preventing alveolar collapse at low lung volumes.
Sterols are represented by cholesterol, which has an important role in the overall structure and motion of the lipids as a whole, but is vastly outnumbered by the phospholipids in surfactant.
Other lipids found commonly in surfactant include phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylethanolamine (PE), and phosphatidylserine (PS).
They are hydrophilic, so they are found in the solution, and function in immune response instead of lipid arrangement and surface tension reduction.