TABLE 1.

Classification of Hsp into families according to their molecular mass

Namea	Mass (kDa)	Found in archaea
Heavy (high mol wt, Hsp100)	100 or higher	Nob
Hsp90	81–99	No
Hsp70 (chaperones)	65–80	Yes
Hsp60 (chaperonins)	55–64	Yes
Hsp40(DnaJ)	35–54	Yes
Small Hsp (sHsp)	<35	Yes
Other (proteases, etc.)	Various	Yes

^aSynonyms are given in parentheses. For additional information and a brief history, see references 103, 177, and 235 and references therein. 

^bNot yet investigated, or investigated but not yet found, or found but incompletely characterized (see also references 47 and 152).