Titre
Kinetics of the cooperative association of T4 tail sheath protein P18 to polysheaths.
Type
article
Institution
Externe
Périodique
Auteur(s)
Tschopp, J.
Auteure/Auteur
Engel, J.
Auteure/Auteur
Liens vers les personnes
ISSN
0301-4622
Statut éditorial
Publié
Date de publication
1980
Volume
12
Numéro
3-4
Première page
307
Dernière page/numéro d’article
315
Langue
anglais
Résumé
The polymerization of the monomeric sheath protein P18 to polysheath was followed by light scattering in 1 mM sodium phosphate buffer, pH 7 at a MgCl2 concentration of 5 mM. Sigmoidal kinetics were observed in the case of spontaneous nucleation. These were well fitted by a mechanism involving a slow nucleation step (rate constant kN = 10(-2) M-1 S-1) followed by propagation steps (k = 10(5) M-1 S-1) in which P18 protomers are added to the ends of the polysheath particles. When sonicated polysheaths or contracted sheaths were added as seeds exponential time courses were observed. From the pseudo first order rate constant and the concentration of seeds the above value for the rate constant of propagation was confirmed. The ability of contracted sheaths to nucleate polysheath formation lends support to the conclusion that polysheaths and contracted sheaths have identical structures and differ in their length distributions only. These were measured from electromicrographs and from the distribution of sedimentation coefficients. Poisson type, kinetically controlled size distributions were found after polymerization of polysheath. An extremely slow redistribution towards an exponential distribution was detected. The spontaneous slow formation of polysheaths is much slower than the formation of extended sheath are core baseplates. Extended sheath is a metastable assembly produce of P18 which either dissociates of contracts to form contracted sheath. Polysheaths and contracted sheaths are extremely stable products but their immediate formation is hindered by high nucleation difficulties.
PID Serval
serval:BIB_A29417BA97AB
PMID
Date de création
2008-01-24T14:19:14.652Z
Date de création dans IRIS
2025-05-20T21:09:38Z