Biologia, Bratislava, 57/Suppl. 11: 43-57, 2002.
ISSN 0006-3088 (Biologia).
Unitat de Biotecnologia Computacional, Departament de Bioquímica i Biotecnologia, Universitat Rovira i Virgili, Plaça de la Imperial Tàrraco, 1. Tarragona 43005, Catalonia (Spain); tel.: ++ 34 977 55 95 65, fax: ++ 34 977 55 95 97, e-mail: email@example.com
Received: October 29, 2001 / Accepted: February 12, 2002
57/Suppl. 10: xxx-xxx, 2002; ISSN 0006-3088 (Biologia). ISSN 1335-6399
(Biologia. Section Cellular and Molecular Biology).
the activities of the
a-amylase family of enzymes are different,
they have a common ancestor. Their polypeptide chain always has a multi-domain
arrangement (though the number of domains usually depends on the enzyme activity).
The domains that we call A and B are always found in these structures. The A
domain, which is the catalytic domain, is always a TIM-barrel fold. The B
domain varies in sequence length and fold, and lies between the third b-strand and the third a-helix of
the A domain. Its function has not yet been fully established. To determine
whether the variability of the B domain affects the folding of the A domain, we
studied the geometrical characteristics of the eight-stranded b-sheet at the core of the A domain. Our results show that
the geometry of the TIM barrel does not depend on the length or fold of the B
domain and supports the idea of an independent folding pathway for the A and B
domains in a-amylase enzymes. Unwanted mutations that
produce a different barrel geometry may be recognised by molecular chaperones
and discarded as functional molecules. Our results show that family 77 enzymes
have the same barrel geometry as family 13 enzymes. This supports the
hypothesis that they have a common origin.
b/a barrel, TIM barrel, a--amylase family, family 13 glycoside hydrolases, family 77
glycoside hydrolases, clan GH-H, chaperones.