ISSN:
0887-3585
Keywords:
homologous proteins
;
hydropathy index
;
chain flexibility
;
α/β barrels
;
tryptophan
;
synthase aplha subunit
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
The amino acid sequences of the α subunits of tryptophan synthase form ten different microorganisms were alingned by standard procedures. The α helics, β strands and turns of each sequence were predicted separately by two standard prediction algorithms and averaged at homologous sequence positions. Additional evidence for conserved secondary structure was derived form profiles of average hydropathy and chain flexibility values, leading to a joint prediction. There is good agreement between (1) predicted β strands, maximal hydropathy and minimal flexibility, and (2) predicted loops, great chain flexibility, and protein segments that accept insertions of various lengths in individual sequences. The α subunit is predicted to have eight repeated β-loop-α-loop motifs with an extra N-terminal α helix and an intercalated segment of highly conserved residues. This pattern suggests that the teritiary structure of the α subunit is an eightfold α/β barrel. The distribution of conserved amino acid residues and publilshed data on limited proteolysis, chemical modification, and mutagenesis are consistent with the α/β barrel structure. Both the active site of the α subunit and the combining site for the β2 subunit are at the end of the barrel formed by the carboxyl-termini of the β strands.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/prot.340020206
Permalink
