The residues from monomer A (N308, G312, C314, F313, S333, G334, G335, S336) and monomer B (S327, F328 and E329) are interacting with lysine in the crystal structure of CaAK ( Fig. 7B). Lysine–protein interactions pattern more similar in the lysine bound structures of EcAKIII (PDB 2J0X) and AtAK (PDB 2CDK) than the threonine bound structure MjAK (PDB ID 3C1N). In the structure of EcAKIII, the residues M318, S321, G323, F324, L325, T344, S345, G346 from monomer A and residues S338, V339, D340 from monomer B are involved in selleck chemicals lysine binding ( Fig. 7C). The mutational analysis of EcAKIII detected two amino acid residue regions (318–325 and 345–352) that may be important in feedback inhibition in EcAKIII

[39]. On comparison essential/conserved residues between the structures of CaAK and ABT-199 price EcAKIII reveals that the residue C314 might play an important role in binding the lysine in CaAK structure. Recently, insilico studies combined with co-evolutionary analysis on EcAKIII further confirmed the previous studies and helped to identify the network of residues involved in allosteric regulation [40]. The multiple sequence alignment of CaAK against class I AKs suggests that the catalytic activity and aspartate binding residues are fully conserved. Previous site directed mutagenesis and crystallographic studies of EcAKIII identified

two residues, K8 and D202, that appear to play roles in the enzymatic activity while residues E119 and R198 are involved in the binding of amino acid substrate, having interactions with the α-NH3+ and α-COO− groups of aspartate, respectively [41]. Interestingly, the multiple sequence alignment of CaAK on EcAKIII suggests that corresponding residues K7 (K8 of AKIII), D188 (D202 of AKIII), E116 (E119 of AKIII) and R184 (R198 of AKIII) are fully conserved ( Fig. 1) in CaAK. The aspartate binding environment of CaAK is homologous to other class I AKs.

Most of the residues Racecadotril at the domain crossover regions (W208–G213 and E237–I250) are also conserved (Fig. 4B). In the crystal structure of MjAK, the residues D239 and R241 are involved in binding to nucleotide. The sequence alignment shows that the corresponding residues D216 and R218 are conserved in CaAK ( Fig. 1). In the structure of CaAK the residues at nucleotide binding region shows disorder. The residues from Y239 to L245 are not visible in the electron density map for the chains A, C, F, G, I, K and L whereas for the chains B, D, H and J these residues are visible with elevated temperature factors without the side chains for some of the residues. This observation suggests that the nucleotide binding to CaAK will be similar to that of MjAK. The main differences between all class I AK structures are with relative orientation of the sub-domains and variable length of the latch loop between the catalytic and regulatory domains.