Blocking creatine kinase refolding by trace amounts of copper ions

Proteomic analysis of methyl parathion-responsive proteins in zebrafish (Danio rerio) brain

Methyl parathion (MP), an organophosphorus pesticide used worldwide, has been associated with a wide spectrum of toxic effects on organisms in the environment. This study set out to analyze the alteration of protein profiles in MP-exposed zebrafish (Danio rerio) brain and find the proteins responsive to MP toxicity. Zebrafish were subjected to 1, 3 and 5mg/L MP and the proteomic changes in their brains were revealed using two-dimensional gel electrophoresis. Six protein spots were observed to be significantly changed by MP exposure. Among these, 4 spots were down-regulated, while 2 spots were up-regulated. These altered spots were excised from the gels and identified by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry and database searching. The results indicate that these proteins were involved in binding, catalysis, regulation of energy metabolism and cell structure. These data may provide novel biomarkers for the evaluation of MP contamination and useful insights for understanding the mechanisms of MP toxicity.

Dissecting the key residues crucial for the species-specific thermostability of muscle-type creatine kinase

Species-specific protein thermal stability is closely correlated to the living conditions of the organism, especially to its body temperature. In this research, human and zebrafish muscle-type creatine kinases (MMCKs) were taken as model proteins to investigate the molecular adaptation of proteins in poikilothermal and homoiothermal animals. Both the optimal temperature for catalysis and the thermal stability of human MMCK was much higher than those of zebrafish MMCK. Sequence alignment identified 9 amino acid variations conserved in either the teleost MMCKs or the mammal and electric ray MMCKs. Bidirectional mutations were performed to find the residues with beneficial mutations. The results showed that two residues close to the dimer interface of MMCK, the 46th and 146th residue, were crucial for species-specific thermal stability.

Sequential events in the irreversible thermal denaturation of human brain-type creatine kinase by spectroscopic methods

The non-cooperative or sequential events which occur during protein thermal denaturation are closely correlated with protein folding, stability, and physiological functions. In this research, the sequential events of human brain-type creatine kinase (hBBCK) thermal denaturation were studied by differential scanning calorimetry (DSC), CD, and intrinsic fluorescence spectroscopy. DSC experiments revealed that the thermal denaturation of hBBCK was calorimetrically irreversible. The existence of several endothermic peaks suggested that the denaturation involved stepwise conformational changes, which were further verified by the discrepancy in the transition curves obtained from various spectroscopic probes. During heating, the disruption of the active site structure occurred prior to the secondary and tertiary structural changes. The thermal unfolding and aggregation of hBBCK was found to occur through sequential events. This is quite different from that of muscle-type CK (MMCK). The results herein suggest that BBCK and MMCK undergo quite dissimilar thermal unfolding pathways, although they are highly conserved in the primary and tertiary structures. A minor difference in structure might endow the isoenzymes dissimilar local stabilities in structure, which further contribute to isoenzyme-specific thermal stabilities.

Mutation of the conserved Asp122 in the linker impedes creatine kinase reactivation and refolding

Creatine kinase (CK), a key enzyme in maintaining the intracellular energetic homeostasis, contains two domains connected by a long linker. In this research,we found that the mutations of the conserved Asp122 in the linker slightly affected CK activity, structure and stability. The hydrogen bonding and the ion pair contributed 2-5 kJ/mol to the conformational stability of CK. Interestingly, the ability of CK reactivation from the denatured state was completely removed by the mutations. These results suggested that the electrostatic interactions were crucial to the action of the linker in CK reactivation.

Metabolic biomarkers related to energy metabolism in Saudi autistic children

OBJECTIVES

Energy metabolism is usually manipulated in many neurodegenerative diseases. Autism is considered a definable systemic disorder resulting in a number of diverse factors that may affect the brain development and functions both pre and post natal. The increased prevalence of autism will have enormous future public implications and has stimulated intense research into potential etiologic factors. This study aims to establish a connection between autism and the deterioration accompanied it, especially in the brain cognitive areas through a postulation of energy manipulation.

MATERIALS AND METHODS

The biochemical changes in activities of enzymes and pathways that participate in the production of ATP as the most important high-energy compound needed by the human brain were measured in Saudi autistic children. Na(+)/K(+)ATPase, ectonucleotidases (NTPDases) (ADPase and ATPase) and creatine kinase (CK), were assessed in plasma of 30 Saudi autistic patients and compared to 30 age-matching control samples. In addition, adenosine mono, di and trinucleotides (ATP, ADP, and AMP) were measured calorimetrically in the red blood cells of both groups and the adenylate energy charge (AEC) was calculated. Moreover, lactate concentration in plasma of both groups was monitored.

RESULTS

The obtained data recorded 148.77% and 72.35% higher activities of Na(+)/K(+)ATPase and CK respectively in autistic patients which prove the impairment of energy metabolism in these children compared to age and sex matching healthy controls. While ADPase was significantly higher in autistic patients, ATPase were non-significantly elevated compared to control. In spite of the significant increase of Na(+)/K(+)ATPase activity in autistic patients, there was no significant difference in the levels of ATP, ADP, and AMP in both groups and the calculated AEC values were 0.814+/-0.094 and 0.806+/-0.081 for autistic and control groups respectively. The unchanged AEC value in autistic patients was easily correlated with the induced activity of CK and ADPase as two enzymes playing a critical role in the stabilization of AEC. Lactate as an important energy metabolite for the brain was significantly higher in autistic patients compared to control showing about 40% increase.

CONCLUSION

The present study confirmed the impairment of energy metabolism in Saudi autistic patients which could be correlated to the oxidative stress previously recorded in the same investigated samples. The identification of biochemical markers related to autism would be advantageous for earlier clinical diagnosis and intervention.