RESUMEN
Chaperonins from psychrophilic bacteria have been shown to exist as single-ring complexes. This deviation from the standard double-ring structure has been thought to be a beneficial adaptation to the cold environment. Here we show that Cpn60 from the psychrophile Pseudoalteromonas haloplanktis (Ph) maintains its double-ring structure also in the cold. A strongly reduced ATPase activity keeps the chaperonin in an energy-saving dormant state, until binding of client protein activates it. Ph Cpn60 in complex with co-chaperonin Ph Cpn10 efficiently assists in protein folding up to 55 °C. Moreover, we show that recombinant expression of Ph Cpn60 can provide its host Escherichia coli with improved viability under low temperature growth conditions. These properties of the Ph chaperonin may make it a valuable tool in the folding and stabilization of psychrophilic proteins.
Asunto(s)
Proteínas Bacterianas , Frío , Escherichia coli , Pliegue de Proteína , Pseudoalteromonas , Pseudoalteromonas/genética , Pseudoalteromonas/metabolismo , Proteínas Bacterianas/metabolismo , Proteínas Bacterianas/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Chaperonina 60/metabolismo , Chaperonina 60/genética , Chaperonina 60/química , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/química , Chaperoninas/metabolismo , Chaperoninas/genética , Chaperoninas/química , Adenosina Trifosfatasas/metabolismo , Adenosina Trifosfatasas/genéticaRESUMEN
ß-Propellers arise through the amplification of a supersecondary structure element called a blade. This process produces toroids of between four and twelve repeats, which are almost always arranged sequentially in a single polypeptide chain. We found that new propellers evolve continuously by amplification from single blades. We therefore investigated whether such nascent propellers can fold as homo-oligomers before they have been fully amplified within a single chain. One- to six-bladed building blocks derived from two seven-bladed WD40 propellers yielded stable homo-oligomers with six to nine blades, depending on the size of the building block. High-resolution structures for tetramers of two blades, trimers of three blades, and dimers of four and five blades, respectively, show structurally diverse propellers and include a novel fold, highlighting the inherent flexibility of the WD40 blade. Our data support the hypothesis that subdomain-sized fragments can provide structural versatility in the evolution of new proteins.
