Domain complementation studies reveal residues critical for the activity of the mannitol permease from Escherichia coli

This paper presents domain complementation studies in the mannitol transporter, EIImtl, from Escherichia coli. EIImtl is responsible for the transport and concomitant phosphorylation of mannitol over the cytoplasmic membrane. By using tryptophan-less EIImtl as a basis, each of the four phenylalanines located in the cytoplasmic loop between putative transmembrane helices II and III in the membrane-embedded C domain were replaced by tryptophan, yielding the mutants W97, W114, W126, and W133. Except for W97, these single-tryptophan mutants exhibited a high, wild-type-like, binding affinity for mannitol. Of the four mutants, only W114 showed a high mannitol phosphorylation activity. EIImtl is functional as a dimer and the effect of these mutations on the oligomeric activity was investigated via heterodimer formation (C/C domain complementation studies). The low phosphorylation activities of W126 and W133 could be increased 7–28 fold by forming heterodimers with either the C domain of W97 (IICmtlW97) or the inactive EIImtl mutant G196D. W126 and W133, on the other hand, did not complement each other. This study points towards a role of positions 97, 126 and 133 in the oligomeric activation of EIImtl. The involvement of specific residue positions in the oligomeric functioning of a sugar-translocating EII protein has not been presented before.

Genome-wide association analyses of physical activity and sedentary behavior provide insights into underlying mechanisms and roles in disease prevention.

Although physical activity and sedentary behavior are moderately heritable, little is known about the mechanisms that influence these traits. Combining data for up to 703,901 individuals from 51 studies in a multi-ancestry meta-analysis of genome-wide association studies yields 99 loci that associate with self-reported moderate-to-vigorous intensity physical activity during leisure time (MVPA), leisure screen time (LST) and/or sedentary behavior at work. Loci associated with LST are enriched for genes whose expression in skeletal muscle is altered by resistance training. A missense variant in ACTN3 makes the alpha-actinin-3 filaments more flexible, resulting in lower maximal force in isolated type IIA muscle fibers, and possibly protection from exercise-induced muscle damage. Finally, Mendelian randomization analyses show that beneficial effects of lower LST and higher MVPA on several risk factors and diseases are mediated or confounded by body mass index (BMI). Our results provide insights into physical activity mechanisms and its role in disease prevention

Genome-wide association analyses of physical activity and sedentary behavior provide insights into underlying mechanisms and roles in disease prevention.

Although physical activity and sedentary behavior are moderately heritable, little is known about the mechanisms that influence these traits. Combining data for up to 703,901 individuals from 51 studies in a multi-ancestry meta-analysis of genome-wide association studies yields 99 loci that associate with self-reported moderate-to-vigorous intensity physical activity during leisure time (MVPA), leisure screen time (LST) and/or sedentary behavior at work. Loci associated with LST are enriched for genes whose expression in skeletal muscle is altered by resistance training. A missense variant in ACTN3 makes the alpha-actinin-3 filaments more flexible, resulting in lower maximal force in isolated type II <sub>A</sub> muscle fibers, and possibly protection from exercise-induced muscle damage. Finally, Mendelian randomization analyses show that beneficial effects of lower LST and higher MVPA on several risk factors and diseases are mediated or confounded by body mass index (BMI). Our results provide insights into physical activity mechanisms and its role in disease prevention