Divergent β-hairpins determine double-strand versus single-strand substrate recognition of human AlkB-homologues 2 and 3

Human AlkB homologues ABH2 and ABH3 repair 1-methyladenine and 3-methylcytosine in DNA/RNA by oxidative demethylation. The enzymes have similar overall folds and active sites, but are functionally divergent. ABH2 efficiently demethylates both single- and double-stranded (ds) DNA, whereas ABH3 has a strong preference for single-stranded DNA and RNA. We find that divergent F1 β-hairpins in proximity of the active sites of ABH2 and ABH3 are central for substrate specificities. Swapping F1 hairpins between the enzymes resulted in hybrid proteins resembling the donor proteins. Surprisingly, mutation of the intercalating residue F102 had little effect on activity, while the double mutant V101A/F102A was catalytically impaired. These residues form part of an important hydrophobic network only present in ABH2. In this functionally important network, F124 stacks with the flipped out base while L157 apparently functions as a buffer stop to position the lesion in the catalytic pocket for repair. F1 in ABH3 contains charged and polar residues preventing use of dsDNA substrate. Thus, E123 in ABH3 corresponds to F102 in ABH2 and the E123F-variant gained capacity to repair dsDNA with no loss in single strand repair capacity. In conclusion, divergent sequences outside of the active site determine substrate specificities of ABH2 and ABH3

The Multidimensional Work Motivation Scale: Validation evidence in seven languages and nine countries

Self-determination theory proposes a multidimensional conceptualization of motivation comprising autonomous and controlled forms. Whereas autonomous motivation relates positively to individuals’ optimal functioning (e.g., well-being, performance), controlled motivation is less beneficial. To be able to use self-determination theory in the field of organizational behaviour, the Multidimensional Work Motivation Scale was developed and tested using data from 3435 workers in seven languages and nine countries. Factorial analyses indicated that the 19-item scale has the same factor structure across the seven languages. Convergent and discriminant validity tests across the countries also indicate that the psychological needs for autonomy, competence, and relatedness as well as the theoretically derived antecedents to work motivation (e.g., leadership and job design) are predictably related to the different forms of motivation, which in turn are predictably related to important work outcomes (e.g., well-being, commitment, performance, and turnover intentions). Implications for the development of organizational research based on self-determination theory are discussed