Unfolding of the native conformation of pancreatic ribonuclease disrupts certain intramolecular associations of amino acids involving tyrosine residues (1) ; the subsequent absorbance changes serve as an index of the extent of denaturation of the enzyme (2). Of the 6 tyrosine residues of RNase A, 3 display distinct spectral properties which may be evaluated by determination of changes in ultrav...

Male "viable motheaten" (me(v)) mice, with a naturally occurring mutation in the gene of the SH2 domain protein tyrosine phosphatase SHP-1, are sterile. Known defects in sperm maturation in these mice correlate with an impaired differentiation of the epididymis, which has similarities to the phenotype of mice with a targeted inactivation of the Ros receptor tyrosine kinase. Ros and SHP-1 are co...

The nuclear p68 RNA helicase is essential for normal cell growth. The protein plays a very important role in early organ development and maturation. In our previous report, we showed that recombinant p68 RNA helicase was phosphorylated at serine/threonine and tyrosine residue(s). In the present study, we examined the phosphorylation status of p68 in six different cancer cell lines and compared ...

Src homology region 2 (SH2) domain-containing phosphatase-1 (SHP-1) is a cytosolic protein tyrosine phosphatase containing two SH2 domains in its NH2 terminus. That immunological abnormalities of the motheaten and viable motheaten mice are caused by mutations in the gene encoding SHP-1 indicates that SHP-1 plays important roles in lymphocyte differentiation, proliferation, and activation. To el...

Two classes of compounds have been investigated as inhibitors of purified beef adrenal tyrosine hydroxylase. Among the aromatic amino acids tyrosine analogues were found to be most potent, particularly those having an a-methyl or 3-halogen substitution. Two normal metabolites, monoand diiodo-tyrosine, were found to bevery effective inhibitors. Inhibition by the amino acid analogues was shown to...

Modulation of protein kinase FA/glycogen synthase kinase-3alpha (kinase FA/GSK-3alpha) by reversible tyrosine phosphorylation/dephosphorylation was investigated. In addition to genistein, other protein tyrosine kinase (PTK) inhibitors, such as tyrphostin A47 and B42, also could induce tyrosine dephosphorylation and inactivation of kinase FA/GSK-3alpha in A431 cells, and this process was found t...

A series of 4-amino-6-benzimidazole-pyrimidines was designed to target lymphocyte-specific tyrosine kinase (Lck), a member of the Src kinase family. Highly efficient parallel syntheses were devised to prepare analogues for SAR studies. A number of these 4-amino-6-benzimidazole-pyrimidines exhibited single-digit nanomolar IC(50)s against Lck in biochemical and cellular assays. These 4-amino-6-be...

The induction of epidermal differentiation by extracellular Ca2+ involves activation of both tyrosine kinase and protein kinase C (PKC) signaling cascades. To determine if the differentiation-dependent activation of tyrosine kinase signaling can influence the PKC pathway, we examined the tyrosine phosphorylation status of PKC isoforms in primary mouse keratinocytes stimulated to terminally diff...

Bruton’s tyrosine kinase (BTK) mediated signaling is critical for B cell development and activation. The physiological role of BTK is evident since its functional loss results in a differentiation block of B cells beyond the pro-B cell stage causing X-linked agammaglobulinemia. Inhibitors of BTK, such as ibrutinib and acalabrutinib profoundly impair BCR signaling. They are highly effective in t...