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T Kurth

Publications and source records attributed to T Kurth.

25 records · Page 2Linked to original sources
PubMed1997

Converting trypsin to chymotrypsin: structural determinants of S1' specificity.

Trypsin and chymotrypsin differ strikingly in substrate specificities despite great similarity in their primary and tertiary structures. This work analyzes the role of two surface loops, loop 40 and loop 60, as structural determinants of the specificity of the S1'-subsite in chymotrypsin and trypsin. Chymotrypsin prefers P1' Arg/Lys residues, while trypsin prefers hydrophobic P1' residues. We replaced loop 40 and loop 60 in trypsin with their chymotrypsin counterparts. These mutations do not affect the S1 specificity and catalytic activity of trypsin. The S1' specificity was analyzed by monitoring acyl-transfer reactions to 16 amino acid amides. The exchange of loop 40 does not affect the S1' specificity. In contrast, the replacement of loop 60 causes a loss of specificity for P1'-Met/Ile/Leu. Combining both mutations reconstitutes a chymotrypsin-like S1' specificity. The specificity for Arg-NH2 increases 3-fold while the preferences for Met-NH2 and Ile-NH2 decrease 4- and 8-fold, respectively. Therefore, P1'-Arg/Met discrimination changes by factor 12 and P1'-Arg/Ile discrimination changes by factor 24. Thus, loop 40 and loop 60 act synergistically to determine S1' specificity in trypsin and chymotrypsin.

Amino Acid Sequence↗
PubMed1996

Fine structural immunocytochemistry of catenins in amphibian and mammalian muscle.

In adherens junctions, alpha- and beta-catenin serve to link cadherins to the cortical cytoskeleton. Immunofluorescence and immuno-electron microscopy have been applied to elucidate the nature and localization of cadherin/catenin-mediated cell-cell adhesion sites in adult muscle tissues. Antibodies against alpha- and beta-catenin have been used as indicators of such sites in amphibian and mammalian muscle. Intercalated discs are prominent cell-cell adhesion sites in heart muscle. They contain large amounts of the two catenins, the distributions of which are disclosed. In addition and in contrast to their counterparts in guinea pig, cardiomyocytes of Xenopus are also interconnected laterally by catenin-containing cell-cell junctions. These are doublet structures that approach the intercellular contacts of two adjacent cells from both sides and occur in register with the Z-discs. We interpret these structures as catenin/cadherin-based costameres. Ultrastructural details of these structures are described. In addition to its presence in cell-cell adhesion sites, we have found beta-catenin, but not alpha-catenin, in the Z-discs of heart and skeletal striated muscles. In smooth muscle, actin filaments insert into the dense bodies, which are therefore regarded as functional equivalents of the Z-discs. Accordingly, beta-catenin is also found in these structures, again in the absence of alpha-catenin. These non-peripheral intracellular localizations in the Z-discs of striated muscles and the dense bodies of smooth muscle indicate a hitherto unknown function of beta-catenin in these specialized cells.

Animals↗