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Phosphotyrosyl protein phosphatases play an important role in mediating cellular
signal transduction; yet three-dimensional structures of this important class of
proteins have not been reported. We present the sequence-specific 1H, 13C, and
15N backbone assignments for the low molecular weight bovine heart
phosphotyrosyl protein phosphatase (BHPTPase) (157 residues, 17,900). The
assignments were obtained from a combination of double- and triple-resonance
multidimensional NMR experiments. From these assignments, the secondary
structure of BHPTPase was determined from an analysis of NOE patterns, 3JHNH
alpha coupling constants, 13C alpha and 13CO chemical shifts, and amide 1H
exchange rates. BHPTPase was found to consist of a four-stranded parallel
beta-sheet (residues K6-C12, W39-A45, Y87-M91, and K112-L116), four
alpha-helices (residues I21-D32, R58-G67, S94-N104, and D135-R157), and one
stretch of beta 10-helix (residues K79-F85). The secondary structure is
characteristic of the beta alpha beta structural motif. The secondary structure
elements identified in this study are consistent with previous chemical and
mutagenesis studies of BHPTPase structure.
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