2010م - 1444هـ
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Purification of Archaeal Chaperonin

from Sulfolobus shibatae

Elsie Quaite-Randall and Andrzej Joachimiak

1. Introduction

Sulfolobus shibatae is a hyperthermophilic archaeon that was first identified

living in acidic geothermal hot springs. This organism grows optimally at pH

3.0–4.0 and 83°C (1), however it grows over the temperature range of 75–

85°C. When S. shibatae is subjected to higher temperatures (85–90°C) a heatshock response is observed and the major protein induced is a large ring

structure TF55 (2), also called archaeosome (3) or rosettasome (4), which is

composed of two different subunits (4), designated _ and ` (3,4). Apart from

the presence of two subunits, another difference between this molecule and the

prokaryotic GroEL is the number of subunits per ring. In S. shibatae, nine

subunits form each ring compared with seven in GroEL.

The similarity of this double ring (2,3) to that of GroEL, together with the

fact that the subunits were 60 kDa, it was a heat-shock protein, and it was

active in protein folding, suggested that it was the archaeal chaperonin (2) and

was similar in function to GroEL. However, comparison of the primary structure showed that both subunits were more closely related to the TCP-1 family

of polypeptides, the eukaryotic cytosolic chaperonin (2,4,5). In contrast to the

archaeal chaperonin, the eukaryotic cytosolic chaperonin comprises eight

sequence-related polypeptides, which also form the characteristic “double

doughnut.” The archaeal chaperonin therefore gives us a simplified version of

the eukaryotic chaperonin by which it may be possible to determine characteristics of the eukaryotic chaperonin. Archaeal and mammalian cytoplasmic

chaperonins are often referred to as Type II chaperonins. The chaperonin from

S. shibatae is a Type II chaperonin (6) and is related, by primary sequence