DHHC domain | |||||||||
---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||
Symbol | DHHC | ||||||||
Pfam | PF01529 | ||||||||
InterPro | IPR001594 | ||||||||
PROSITE | PDOC50216 | ||||||||
OPM superfamily | 476 | ||||||||
OPM protein | 6bmm | ||||||||
|
In molecular biology the DHHC domain is a protein domain that acts as an enzyme, which adds a palmitoyl chemical group to proteins in order to anchor them to cell membranes. The DHHC domain was discovered in 1999 and named after a conserved sequence motif found in its protein sequence. [1] Roth and colleagues showed that the yeast Akr1p protein could palmitoylate Yck2p in vitro and inferred that the DHHC domain defined a large family of palmitoyltransferases. [2] In mammals twenty three members of this family have been identified and their substrate specificities investigated. [3] Some members of the family such as ZDHHC3 and ZDHHC7 enhance palmitoylation of proteins such as PSD-95, SNAP-25, GAP43, Gαs. Others such as ZDHHC9 showed specificity only toward the H-Ras protein. [3] However, a recent study questions the involvement of classical enzyme-substrate recognition and specificity in the palmitoylation reaction. [4] Several members of the family have been implicated in human diseases.
Conserved motifs within protein sequences point towards the most important amino acid residues for function. In the DHHC domain there is a tetrapeptide motif composed of aspartate-histidine-histidine-cysteine. However this short sequence is embedded in a larger region of about fifty amino acids in length that shares many more conserved amino acids. The canonical DHHC domain can be described with the following sequence motif:
However many examples of DHHC domains are known that do not contain all these conserved residues. In addition to the central DHHC domain three further sequence motifs have been identified in members of the DHHC family. A DPG (aspartate-proline-glycine) motif has been identified just to the C-terminus of the second transmembrane region. [5] A TTxE (threonine-threonine-any-glutamate) motif has also been identified after the fourth transmembrane helix. [5] A third motif towards the C-terminus of many proteins has been identified that contains a conserved aromatic amino acid, a glycine and an asparagine called the PaCCT motif (PAlmitoiltransferase Conserved C-Terminus motif). [6]
Several structures of the DHHC domain has been solved, and it is known to run on a linearly-arranged catalytic triad of Asp153, His154, and Cys156. It runs on a ping-pong mechanism, where the cysteine attacks the acyl-CoA to form an S-acylated DHHC, and then the acyl group is transferred to the substrate. DHHR enzymes exist, and they (as well as some DHHC enzymes) may use a ternary complex mechanism instead. [7]
In 2006, five chemical classes of small molecules were discovered which were shown to act against palmitoyltransferases. [8] Further studies in 2009 showed that of the 5 classes studied, 2-(2-hydroxy-5-nitro-benzylidene)-benzo[b]thiophen-3-one was shown to behave similarly to 2-Bromopalmitate and were identified as able to inhibit the palmitoylation reaction of a range of DHHC domain containing proteins. Inhibition with 2-Bromopalmitate was found to be irreversible, the other however was found to be mostly reversible. [9] Because of the roles of DHHC domain proteins in human diseases it has been suggested that chemical inhibitors of specific DHHC proteins may be a potential route to treatment of disease. [9]
Several proteins containing DHHC domains have been implicated in human disease. Two missense mutations within the DHHC domain of ZDHHC9 were identified in X-linked mental retardation associated with a Marfanoid Habitus. [10] A potential link of ZDHHC11 with bladder cancer has been suggested by the discovery that 5 out of 9 high-grade bladder cancer samples surveyed contained a duplication of the 5p15.33 genomic region. [11] However, this region contains another gene TPPP which may be the causative gene. The HIP14 palmitoyltransferase is responsible for palmitoylating the Huntingtin protein. Expansions of the triplet repeat in the huntington's gene leads to loss of interaction with HIP14 which Yanai and colleagues speculate is involved in the pathology of Huntington's disease. [12] A gene knockout experiment of the mouse homologue of ZDHHC13 showed hair loss, severe osteoporosis, and systemic amyloidosis, both of AL and AA depositions. [13]
ZDHHC1; ZDHHC2; ZDHHC3; ZDHHC4; ZDHHC5; ZDHHC6; ZDHHC7; ZDHHC8; ZDHHC9; ZDHHC11; ZDHHC11B; ZDHHC12; ZDHHC13; ZDHHC14; ZDHHC15; ZDHHC16; ZDHHC17; ZDHHC18; ZDHHC19; ZDHHC20; ZDHHC21; ZDHHC22; ZDHHC23; ZDHHC24;
Prenylation is the addition of hydrophobic molecules to a protein or a biomolecule. It is usually assumed that prenyl groups (3-methylbut-2-en-1-yl) facilitate attachment to cell membranes, similar to lipid anchors like the GPI anchor, though direct evidence of this has not been observed. Prenyl groups have been shown to be important for protein–protein binding through specialized prenyl-binding domains.
SNARE proteins – "SNAPREceptors" – are a large protein family consisting of at least 24 members in yeasts, more than 60 members in mammalian cells, and some numbers in plants. The primary role of SNARE proteins is to mediate the fusion of vesicles with the target membrane; this notably mediates exocytosis, but can also mediate the fusion of vesicles with membrane-bound compartments. The best studied SNAREs are those that mediate the release of synaptic vesicles containing neurotransmitters in neurons. These neuronal SNAREs are the targets of the neurotoxins responsible for botulism and tetanus produced by certain bacteria.
Carnitine O-palmitoyltransferase is a mitochondrial transferase enzyme involved in the metabolism of palmitoylcarnitine into palmitoyl-CoA. A related transferase is carnitine acyltransferase.
Carnitine palmitoyltransferase I (CPT1) also known as carnitine acyltransferase I, CPTI, CAT1, CoA:carnitine acyl transferase (CCAT), or palmitoylCoA transferase I, is a mitochondrial enzyme responsible for the formation of acyl carnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from coenzyme A to l-carnitine. The product is often palmitoylcarnitine, but other fatty acids may also be substrates. It is part of a family of enzymes called carnitine acyltransferases. This "preparation" allows for subsequent movement of the acyl carnitine from the cytosol into the intermembrane space of mitochondria.
ADP-ribosylation factor-binding protein GGA1 is a protein that in humans is encoded by the GGA1 gene.
Alpha-centractin (yeast) or ARP1 is a protein that in humans is encoded by the ACTR1A gene.
Syntaxin-6 is a protein that in humans is encoded by the STX6 gene.
Golgin subfamily A member 3 is a protein that in humans is encoded by the GOLGA3 gene.
Nucleobindin-1 (NUCB1), also known as calnuc, is a protein that in humans is encoded by the NUCB1 gene.
Cytoskeleton-associated protein 4 is a protein that in humans is encoded by the CKAP4 gene.
DnaJ homolog subfamily C member 5, also known as cysteine string protein or CSP is a protein, that in humans encoded by the DNAJC5 gene. It was first described in 1990.
Golgin subfamily A member 5 is a protein that in humans is encoded by the GOLGA5 gene.
Oxysterol-binding protein 1 is a protein that in humans is encoded by the OSBP gene.
Palmitoyltransferase ZDHHC9 is an enzyme that in humans is encoded by the ZDHHC9 gene that contains a DHHC domain.
Palmitoyltransferase ZDHHC17 is an enzyme that contains a DHHC domain that in humans is encoded by the ZDHHC17 gene.
Rab9 effector protein with Kelch motifs also known as p40 is a protein that in humans is encoded by the RABEPK gene.
The ERM protein family consists of three closely related proteins, ezrin, radixin and moesin. The three paralogs, ezrin, radixin and moesin, are present in vertebrates, whereas other species have only one ERM gene. Therefore, in vertebrates these paralogs likely arose by gene duplication.
Zinc finger, also known as ZDHHC2, is a human gene.
Palmitoyl acyltransferase is a group of enzymes that transfer palmityl group to -SH group on cysteine on a protein. This modification increases the hydrophobicity of the protein, thereby increasing the association to plasma membrane or other intramembraneous compartments.
Acyl-protein thioesterases are enzymes that cleave off lipid modifications on proteins, located on the sulfur atom of cysteine residues linked via a thioester bond. Acyl-protein thioesterases are part of the α/β hydrolase superfamily of proteins and have a conserved catalytic triad. For that reason, acyl-protein thioesterases are also able to hydrolyze oxygen-linked ester bonds.