Structure of Paramecium tetraurelia calmodulin at 1.8 Å resolution

Abstract

The crystal structure of calmodulin (CaM; M, 16,700, 148 residues) from the ciliated protozoan Paramecium tetraurelia (PCaM) has been determined and refined using 1.8 A resolution area detector data. The crystals are regions differ, where the B-factors are also high, particularly in PCaM and MCaM. Unlike the MCaM structure, with one kink at D80 in the middle of the linker region, and the DCaM structure, with two kinks at K75 and 185, in our PCaM structure there are no kinks in the helix; the distortion appears to be more gradually distributed over the entire helical region, which is bent with an apparent radius of curvature of 74.5(2) A. The different distortions in the central helical region probably arise from its inherent mobility.

Correlated mutations contain information about protein-protein interaction 1 1Edited by A. R. Fersht

“…In two crystal forms of calmodulin (PDB code 3cln (Babu et al, 1988) and 1clm (Rao et al, 1993)) the two protein domains do not interact, the closest residues belonging to different domains are more than 24 A Ê apart. When using this structure to calculate the distance distributions, correlated mutations cannot be much closer than the rest of the residues, and in fact the Xd value is only 2.19 (Table 1 and Figure 2(a)).…”

Molecular Tuning of Ion Binding to Calcium Signaling Proteins

“…Bound calcium ions are shown in yellow, and the conserved glycine at position 6 in the EF-loop, which acts as a hinge, is highlighted by a CPK sphere on its a-carbon. The backbone atoms of loop residues i-6 were superimposed for all 35 EF-hand structures, yielding an average RMS deviation of 0-27 A. Ca 2+ -loaded sites from the following structures were used: calmodulin sites I through IV from human (Chattopadhyaya et al 1992), Paramecium (Rao et al 1993;Ban et al to be published), rat (Babu et al 1988), and Drosophila (Taylor et al 1991); troponin C (sites III & IV) from chicken (Satyshur et al 1988) and turkey (Herzberg & James, 1988); parvalbumin (CD and EF sites) from shark (Roquet et al 1992) and carp (Kumar et al 1990, Swain et al 1989); E. coli galactose-glucose binding protein (1 site) (Vyas et al 1988). Apo sites I and II of troponin C were from the above referenced TnC structures.…”

Structure of a Trapped Intermediate of Calmodulin: Calcium Regulation of EF-hand Proteins from a New Perspective

“…2 The 3D structure of the Ca 2C -bound form of CaM from bovine brain has been known since 1985. 3,4 More recently the structures of CaM from Homo sapiens, 5 Paramecium tetraurelia 6 and Drosophila melanogaster 7 were published. In a recent publication a detailed picture of the intramolecular atomic dynamics in CaM was presented based on 1 Å resolution X-ray data.…”