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Category: Bacterial Pathogenesis; Microbial Genetics and Molecular Biology
Spore Structural Proteins, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818388/9781555810535_Chap55-1.gif /docserver/preview/fulltext/10.1128/9781555818388/9781555810535_Chap55-2.gifAbstract:
Each spore coat and nucleoid structure contains a large amount of protein, with spore coats comprising ~50% and spore nucleoid proteins greater than are equal to 5% of total Bacillus subtilis spore protein; spores of other Bacillus species have comparable amounts of protein in these two structures. Thus, both spore coat and spore nucleoid components are major spore structural proteins; both types of proteins consist of multiple species coded for by monocistronic genes scattered around the B. subtilis chromosome. Understanding the structure and function of their individual protein components can give insight into spore coat and nucleoid structures. The majority of the B. subtilis spore coat appears to be composed of protein (~50% of total spore protein), although small amounts of lipid should be present in spore coat preparations, since the outer forespore membrane is often extracted with spore coat proteins. The proteins associated with the spore coat and nucleoid are unique both to the spore stage of the B. subtilis life cycle and also to this group of organisms. A number of the spore coat proteins have highly unusual amino acid compositions that may be important in their specific functions in the complex spore coat. α/ β-Type small acid-soluble spore proteins (SASP), on the other hand, do not have unusual amino acid compositions but have properties in vitro that clearly indicate how these proteins function in determining forespore nucleoid structure and properties in vivo.
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Electron micrograph of a dormant spore of B. subtilis PY79. Sporulation was caused by nutrient exhaustion, and spores were taken at t20 for fixation. Methods for fixation and staining were as described in reference 9 . The outer spore coat (oc), inner spore coat (ic), and spore cortex (cx) layers are noted. Bar for entire spore, 100 nm; bar for enlargement of the coat region, 50 nm.
Electron micrograph of a dormant spore of B. subtilis PY79. Sporulation was caused by nutrient exhaustion, and spores were taken at t20 for fixation. Methods for fixation and staining were as described in reference 9 . The outer spore coat (oc), inner spore coat (ic), and spore cortex (cx) layers are noted. Bar for entire spore, 100 nm; bar for enlargement of the coat region, 50 nm.
Primary sequence of B. subtilis α/β-type SASP. Known amino acid sequences of α/β-type SASP from B. subtilis and the protein specified by the sspF gene (previously 0.3 kb) are shown in one-letter code and are taken from references 49 and 51 . The N-terminal methionine in the coding gene is included but is undoubtedly removed posttranslationally. The sspA gene codes for SASP-α, sspB codes for SASP-β, sspC codes for SspC, and sspD codes for SspD ( 49 ). For the proteins specified by the sspABCD genes, residues conserved in all known α/β-type SASP from the Bacillus line of sporeformers are in boldface type; residues that are similar in these SASP are underlined. A gap has been introduced in these sequences to maximize the alignment with SspF. The large downward-pointing arrow indicates the site of cleavage by the SASP-specific protease ( 49 ). The two upward-pointing arrowheads indicate residues whose alteration in SspC (Gly→Ala or Lys→GIn) reduces or abolishes the ability of this protein to bind DNA in vivo or in vitro ( 57 ). For the protein specified by the sspF gene, residues identical to those conserved in other α/β-type SASP are in boldface; residues similar to those in other α/β-type SASP are underlined.
Primary sequence of B. subtilis α/β-type SASP. Known amino acid sequences of α/β-type SASP from B. subtilis and the protein specified by the sspF gene (previously 0.3 kb) are shown in one-letter code and are taken from references 49 and 51 . The N-terminal methionine in the coding gene is included but is undoubtedly removed posttranslationally. The sspA gene codes for SASP-α, sspB codes for SASP-β, sspC codes for SspC, and sspD codes for SspD ( 49 ). For the proteins specified by the sspABCD genes, residues conserved in all known α/β-type SASP from the Bacillus line of sporeformers are in boldface type; residues that are similar in these SASP are underlined. A gap has been introduced in these sequences to maximize the alignment with SspF. The large downward-pointing arrow indicates the site of cleavage by the SASP-specific protease ( 49 ). The two upward-pointing arrowheads indicate residues whose alteration in SspC (Gly→Ala or Lys→GIn) reduces or abolishes the ability of this protein to bind DNA in vivo or in vitro ( 57 ). For the protein specified by the sspF gene, residues identical to those conserved in other α/β-type SASP are in boldface; residues similar to those in other α/β-type SASP are underlined.
Properties of spore coat proteins a
Properties of spore coat proteins a
Properties of B. subtilis SASPa
Properties of B. subtilis SASPa