Structural wall proteins

Changes in cell-wall protein composition may regulate the molecular architecture of protein networks in a manner that allows new developmental outcomes for both fungal cell adhesion and root colonization. Further investigation of the structure and regulation of SRAP wall proteins will provide a more complete picture of their role in developing ectomycorrhizal tissues. Incompatibility between ectomycorrhizal hyphae and the host roots detected during the initial con-... 

Fig. 2. Examples of the structures of protein domains and repeats. The images were generated using Molscript (Kraulis, 1991). (A) Immunoglobulin domain (PDB identifier ltlk) (Holden et al1992), (B) A zinc finger domain with coordinated zinc ion (PDB identifienlzaa) (Pavletich and Pabo, 1991). (C) A /3-propeller domain composed of seven WD40 repeats (PDB identifier lgp2) (Wall et al., 1995), (D) An elongated domain of variant leucine-rich repeats (PDB identifienllrv) (Peters et al., 1996).

If 15N ammonium citrate was administered, and glutamate, aspartate, and glycine isolated from liver and intestinal wall protein, all showed 15N uptake. From the results of labeling studies, Schoenheimer finished his Edward K.Dunham lectures in Harvard in 1941 with the phrase— the structural materials [of the body] are in a steady state of flux. The classical picture must thus be replaced by one which takes account of the dynamic state of body structure —an idea which has become an integral part of biochemistry since that time, and which was almost totally dependent on the introduction of isotopes for its discovery. 

Lamport40 considered the primary cell-wall to be a single, bagshaped macromolecule having a coherent, cross-linked structure, with bonds both between the hydroxy-L-proline-rich, wall protein extensin and wall polysaccharides, and between individual polysaccharides. 

Primary cell-walls of dicots contain between 5 and 10% of protein that is rich (20%) in hydroxy-L-proline.4,55,228 The wall protein also contains a relatively high content of L-alanine, L-serine, and L-threonine, and this feature is found in such animal structural-proteins as collagen.228 This characteristic, amino acid composition, together with the fact that it is difficult to extract much of the protein from cell walls under nondegra-dative conditions,229 suggests that it has a structural role in the wall.228-230... 

Glycosylated-inositol (GPI)-anchored proteins have also been used to anchor foreign peptides for cell-surface display in S. cerevisiae [55] and Hansenula poly-morpha [56]. Four different gpi genes and their encoded proteins were characterized for the purpose of displaying fusion protein on the cell surface. The FLOl gene encodes the Flolp protein, a lectin-like cell-wall protein thought to form stemlike structures that cover the distance of the cell wall. This protein has also been used to express peptides on the yeast surface [57]. 

The adhesion of cells to surfaces is different from that of proteins and DNA. Cell adhesion and spreading are believed to depend primarily on the hydrophobicity of both cells and surfaces. Cell surface hydrophobicity is usually associated with the presence of fibrillar structures oti cell surfaces and specific cell wall proteins. Adhesion, spreading, and growth of mammalian cells are generally promoted on hydrophilic surfaces ( static 30 40°) [10], while those of bacterial... 

The mechanism of lectin-like cell-cell interactions has been established to explain yeast flocculation (Speers et al., 1998). Lectins are a structurally diverse group of proteins that are capable of binding carbohydrates while zymolectin is an anchored yeast cell wall protein that contains one or more mannose binding sites (Boulton Quain, 2001). This mechanism proposes that specific surface proteins known as zymolectins, which are present on flocculent yeast cells, bind to mannose residues of mannan molecules on neighbouring cell surfaces (Speers et al., 1998). The involvement of this protein-carbohydrate interaction was suggested by Taylor and Orton (Taylor Orton, 1978), as flocculation can be inhibited specifically by mannose. 

Cell wall protein appears to have "structural role. 

High-resolution NMR is a very powerful technique and can be used in a modified form (known as two-dimensional NMR) to establish the structures of proteins (see Chapter 23 on the accompanying website). Figure 21.8 shows the structure of a small protein known as LysM, which binds to bacterial cell walls. It is shown running from hlue at the nitrc en terminus, and it has an antiparallel heta sheet and three alpha helices. 

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