Polygalacturonase: Difference between revisions
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Not all PGs have ten coils in the parallel beta helix. They usually have approximately 10 coils. | Not all PGs have ten coils in the parallel beta helix. They usually have approximately 10 coils. | ||
[[Image:phb.jpg|300px|left|thumb| Nomenclature for structural elements of the parallel beta helix. PB1 is Parallel Beta Sheet 1, T1 is Turn 1, between PB1 and PB2. ]] | |||
== References == | == References == | ||
<references/> | <references/> | ||
Revision as of 23:50, 12 July 2017
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Polygalacturonases (PGs) catalyze the enzymatic depolymerization of pectins – polysaccharides that comprise the plant cell wall. Polymer disassembly of substrates by exo- and endo- PGs is carried out via a hydrolytic mechanism. Degradation of pectins in plant cell walls contributes to ripening of fruits, such as tomatoes and melons (Polygalacturonases: many genes in search of a function). Microbial PGs have been identified to be a part of defense mechanisms because of their role in pathogen attack (crystal structure).
FunctionFunction
Polygalacturonases hydrolyze α-(1-4) – glycosidic bonds between consecutive galacturonic acid residues in polygalacturonic acids. Structural variation has been identified among differing PGs depending on organismal origins and catalytic functions. For example, endo-polygalacturonases produced from Erwinia carotovora demonstrate functional similarity to pectate lyases in that they cleave polygalacturonic acids in a calcium-depended manner via β-elimination (crystal structure).
DiseaseDisease
RelevanceRelevance
Structural highlightsStructural highlights
The secondary structure of PGs is comprised of a ten turn right handed beta helix domain along with two loop regions that together form the substrate-binding cleft, which appears to have a tunnel-like shape. The active site of PGs is found between the two looped regions of the protein. Located within the looped regions are two conserved aspartate residues that are predicted to participate in catalytic activity (crystal structure).
MDY- a right-handed parallel beta helix is a tertiary fold. The secondary structure is the beta and the alpha structure. If you describe how the secondary structure folds in space, that becomes tertiary structure. The secondary structural elements of the core fold of the proteins are only beta structure, the beta strands form parallel beta sheets. There are three main parallel beta sheets, PG's often have a smaller parallel beta sheet of only three-four beta strands.
Not all PGs have ten coils in the parallel beta helix. They usually have approximately 10 coils.
