Linkage between reactivity of sulfhydryl groups and subunit interactions in aspartate transcarbamoylase.

Aspartate Transcarbamoylase of Aeromonas Hydrophila

The reactivity of sulfhydryl groups of bovine cardiac troponin C.

Bovine cardiac troponin C (cTnC) contains 2 cysteine residues, Cys-35 located in the nonfunctional Ca2+-binding loop I and Cys-84 in the N-terminal segment of the central helix. We have studied the reactivity of Cys residues in cTnC with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin (CPM). The latter compound fluoresces only when reacted ...

Purification of aspartate transcarbamoylase from Pseudomonas syringae.

The aspartate transcarbamoylase (ATCase) from Pseudomonas syringae has been purified. The purified enzyme was shown by SDS-PAGE to give two bands. Unambiguous results from N-terminal sequencing suggested that each band represented a homogeneous polypeptide. The M(r) (relative molecular mass) of the polypeptides was estimated to be 47 kDa and 34 kDa. The M(r) of the holoenzyme determined by gel ...

Cooperative interactions in aspartate transcarbamoylase. 1. Hybrids composed of native and chemically inactivated catalytic polypeptide chains.

Hybrids of aspartate transcarbamoylase (EC 2.1.3.2; carbamoylphosphate: L-aspartate carbamoyltransferase) from Escherichia coli containing native (active) and pyridoxylated (inactive) catalytic polypeptide chains were constructed by a procedure involving the reversible acylation of amino groups with 3,4,5,6-tetrahydrophthalic anhydride. This technique exploited the charges contributed by the te...

The thiol group in the catalytic chains of aspartate transcarbamoylase.

The allosteric enzyme aspartate transcarbamoylase (EC 2.1.3.2) was previously shown to consist of two functionally distinct types of polypeptide chains. X-ray diffraction and chemical studies showed that there are six copies of both catalytic (C) and regulatory (R) chains, and that the intact molecular complex (C(6)R(6)) has D(3) symmetry. Organomercurials react preferentially with the four thi...