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Two tyrosines separated by a single amino acid, typically valine or another tyrosine, form a short intra-molecular diphenylether crosslink. [11] This can be crosslinked further by the enzyme extensin peroxidase [12] [13] [14] to form an inter-molecular bridge between extensin molecules and thus form networks and sheets.
Hydroxyproline is a major component of the protein collagen, [3] comprising roughly 13.5% of mammalian collagen. Hydroxyproline and proline play key roles for collagen stability. [4] They permit the sharp twisting of the collagen helix. [5]
In 2001, biologically active hydroxyproline-rich glycopeptides were isolated from tobacco which activated the production of protease inhibitors in a similar way to systemin in tomatoes. [1] Although they are structurally unrelated to systemins, their similar function resulted in them being named hydroxyproline-rich systemins (HypSys).
Additionally, structural proteins (1-5%) are found in most plant cell walls; they are classified as hydroxyproline-rich glycoproteins (HRGP), arabinogalactan proteins (AGP), glycine-rich proteins (GRPs), and proline-rich proteins (PRPs). Each class of glycoprotein is defined by a characteristic, highly repetitive protein sequence.
One example of glycoproteins found in the body is mucins, which are secreted in the mucus of the respiratory and digestive tracts. The sugars when attached to mucins give them considerable water-holding capacity and also make them resistant to proteolysis by digestive enzymes. Glycoproteins are important for white blood cell recognition.
In plant immunology, the hypersensitive response (HR) is a mechanism used by plants to prevent the spread of infection by microbial pathogens.HR is characterized by the rapid death of cells in the local region surrounding an infection and it serves to restrict the growth and spread of pathogens to other parts of the plant.
28.2% (sunlight energy collected by chlorophyll) → 68% is lost in conversion of ATP and NADPH to d-glucose, leaving; 9% (collected as sugar) → 35–40% of sugar is recycled/consumed by the leaf in dark and photo-respiration, leaving; 5.4% net leaf efficiency. Many plants lose much of the remaining energy on growing roots.
The different types of lipid-linked oligosaccharide (LLO) precursor produced in different organisms.. N-linked glycosylation is the attachment of an oligosaccharide, a carbohydrate consisting of several sugar molecules, sometimes also referred to as glycan, to a nitrogen atom (the amide nitrogen of an asparagine (Asn) residue of a protein), in a process called N-glycosylation, studied in ...