title: The ClpP double ring tetradecameric protease exhibits plastic ring-ring interactions, and the N termini of its subunits form flexible loops that are essential for ClpXP and ClpAP complex formation.
abstract: ClpP is a conserved serine-protease with two heptameric rings that enclose a large chamber containing the protease active sites. Each ClpP subunit can be divided into a handle region, which mediates ring-ring interactions, and a head domain. ClpP associates with the hexameric ATPases ClpX and ClpA, which can unfold and translocate substrate proteins through the ClpP axial pores into the protease lumen for degradation. We have determined the x-ray structure of Streptococcus pneumoniae ClpP(A153P) at 2.5 A resolution. The structure revealed two novel features of ClpP which are essential for ClpXP and ClpAP functional activities. First, the Ala --> Pro mutation disrupts the handle region, resulting in an altered ring-ring dimerization interface, which, in conjunction with biochemical data, demonstrates the unusual plasticity of this region. Second, the structure shows the existence of a flexible N-terminal loop in each ClpP subunit. The loops line the axial pores in the ClpP tetradecamer and then protrude from the protease apical surface. The sequence of the N-terminal loop is highly conserved in ClpP across all kingdoms of life. These loops are essential determinants for complex formation between ClpP and ClpX/ClpA. Mutation of several amino acid residues in this loop or the truncation of the loop impairs ClpXP and ClpAP complex formation and prevents the coupling between ClpX/ClpA and ClpP activities.
authors.affiliation: Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Anna
authors.initials: A
authors.lastname: Gribun
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Kimber
authors.forename: Reagan
authors.initials: R
authors.lastname: Ching
authors.forename: Remco
authors.initials: R
authors.lastname: Sprangers
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Fiebig
authors.forename: Walid A
authors.initials: WA
authors.lastname: Houry
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D049071:Endopeptidase Clp / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013296:Streptococcus pneumoniae / Q000201:enzymology / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D012697:Serine Endopeptidases; C501427:ClpP protein, Streptococcus pneumoniae; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities