Articles written in Journal of Biosciences
Volume 2 Issue 3 September 1980 pp 171-179
Activities and a few properties of alkaline phosphatase and 5’-nucleotidase were compared in the developing human placenta. Both the enzymes were mostly membrane-bound and displayed similar developmental patterns with the highest activities at 24/26 weeks of the placenta. L-Phenylalanine, L-tryptophan and L-leucine were inhibitors of alkaline phosphatase, whereas they had no effect on the 5’-nucleotidase. Alkaline phosphatase from a late stage of gestation appeared to be almost heat-stable. An appreciable part of 5’-nucleotidase was also resistant to heat inactivation and this fraction varied with gestational age of the tissue. For both the enzymes, Vmax changed without altering
Volume 8 Issue 1-2 August 1985 pp 451-460
Troponin C is the Ca2+-binding subunit of the troponin complex and is involved in the calcium control of muscle contraction. The X-ray structure of chicken TnC has been determined at 3Å resolution using a single heavy atom derivative and application of a novel phase improvement and phase extension procedure. The protein has an unusual dumbbell-shape with a length of about 70A. The N- and C-domains are connected by a single long α-helix of about 9 turns. Two metal binding sites (the Ca2+-Mg2+ sites) in the C-domain are occupied by metal ions in the crystals and the helix-loop-helix Ca2+ -binding folds are very similar to those in other known Ca2+ -binding proteins. In contrast, the Ca2+ -specific sites in the N-domain appear unoccupied and the two putative Ca2+ -binding folds have a vastly different structural arrangement. The conformational rearrangements in the N-domain upon Ca2+ binding are believed to be the trigger for a cascade of protein-protein interaction alterations which lead to muscle contraction.