The MBOAT (membrane bound O-acyl transferase) family of membrane proteins is a family of various acyltransferase

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

s. All family members contain multiple transmembrane domains and most carry two conserved residues, a conserved

histidine Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated –NH3+ form under biological conditions), a carboxylic acid group (which is in the d ...

(His) embedded in a

hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, t ...

stretch of residues and an

asparagine Asparagine (symbol Asn or N) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the depro ...

(Asn) or histidine within a more

hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are ...

region some 30-50 residues upstream. MBOAT enzymes

catalyze Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

the transfer of an

acyl In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an alkyl group (). In organic chemistry, the acyl group (IUPAC ...

group from an acyl-coenzyme or accessory protein to one of several different substrates. The family is found from

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

to eukaryotes. The family may be grouped into three categories, according to function: #enzymes involved in neutral lipid biosynthesis; #enzymes involved in protein/peptide acylation; #enzymes involved in phospholipid re-modelling.

Structure

The structure for one MBOAT protein, DltB from ''

Streptococcus thermophilus ''Streptococcus thermophilus'' also known as ''Streptococcus salivarius ''subsp.'' thermophilus'' is a gram-positive bacterium, and a fermentative facultative anaerobe, of the '' viridans'' group. It tests negative for cytochrome, oxidase, an ...

'' (), has been solved. DltB performs D-alanylation of cell-wall

teichoic acid Teichoic acids (''cf.'' Greek τεῖχος, ''teīkhos'', "wall", to be specific a fortification wall, as opposed to τοῖχος, ''toīkhos'', a regular wall) are bacterial copolymers of glycerol phosphate or ribitol phosphate and carbohydr ...

. It contains a ring of 11 transmembrane helices surrounding a tunnel that goes through the biological membrane. The tunnel connects to a partner, DltC, which carries the D-alanine to the conserved histidine residue of DltB MBOAT located at the bottom of the funnel. A computational model of human ghrelin ''O''-acyltransferase (GOAT)
Q96T53
revealed a transmembrane channel that facilitates octanoylation of the peptide hormone

ghrelin Ghrelin (; or lenomorelin, INN) is a hormone produced by enteroendocrine cells of the gastrointestinal tract, especially the stomach, and is often called a "hunger hormone" because it increases the drive to eat. Blood levels of ghrelin are hi ...

. DltB and GOAT share structural similarities in their homologous regions, suggesting a common core fold for MBOAT family members.

Human proteins with this domain

References

* {{InterPro content, IPR004299 Enzymes Membrane proteins Protein families