Accelerated FoxP2 Evolution in Echolocating Bats

FOXP2 is a transcription factor implicated in the development and neural control of orofacial coordination, particularly with respect to vocalisation. Observations that orthologues show almost no variation across vertebrates yet differ by two amino acids between humans and chimpanzees have led to speculation that recent evolutionary changes might relate to the emergence of language. Echolocating bats face especially challenging sensorimotor demands, using vocal signals for orientation and often for prey capture. To determine whether mutations in the FoxP2 gene could be associated with echolocation, we sequenced FoxP2 from echolocating and non-echolocating bats as well as a range of other mammal species. We found that contrary to previous reports, FoxP2 is not highly conserved across all nonhuman mammals but is extremely diverse in echolocating bats. We detected divergent selection (a change in selective pressure) at FoxP2 between bats with contrasting sonar systems, suggesting the intriguing possibility of a role for FoxP2 in the evolution and development of echolocation. We speculate that observed accelerated evolution of FoxP2 in bats supports a previously proposed function in sensorimotor coordination

Comparative biochemical characterization of the iron-only nitrogenase and the molybdenum nitrogenase from Rhodobacter capsulatus

Schneider K, Gollan U, Drottboom M, Selsemeier-Voigt S, Müller A. Comparative biochemical characterization of the iron-only nitrogenase and the molybdenum nitrogenase from Rhodobacter capsulatus. EUROPEAN JOURNAL OF BIOCHEMISTRY. 1997;244(3):789-800.The component proteins of the iron-only nitrogenase were isolated from Rhodobacter capsulatus (Delta nifHDK, Delta modABCD strain) and purified in a one-day procedure that included only one column-chromatography step (DEAE-Sephacel). This procedure yielded component 1 (FeFe protein, Rc1(Fe)), which was more than 95% pure, and an approximately 80% pure component 2 (Fe protein, Rc2(Fe)). The highest specific activities, which were achieved at an Rc2(Fe)/Rc1(Fe) molar ratio of 40:1, were 260 (C2H4 from C2H2), 350 (NH3 formation), and 2400 (H-2 evolution) nmol product formed . min(-1). mg protein(-1). The purified FeFe protein contained 26+/-4 Fe atoms; it did not contain Mo, V, or any other heterometal atom. The most significant catalytic property of the iron-only nitrogenase is its high H-2-producing activity, which is much less inhibited by competitive substrates than the activity of the conventional molybdenum nitrogenase. Under optimal conditions for N-2 reduction, the activity ratios (mol N-2 reduced/mol H-2 produced) obtained were 1:1 (molybdenum nitrogenase) and 1:7.5 (iron nitrogenase). The Rc1(Fe) protein has only a very low affinity for C2H2. The K-m value determined (12.5 kPa), was about ninefold higher than the K-m for Rc1(Mo) (1.4 kPa). The proportion of ethane produced from acetylene (catalyzed by the iron nitrogenase), was strictly pH dependent. It corresponded to 5.5% of the amount of ethylene at pH 6.5 and was almost zero at pH values greater than 8.5. In complementation experiments, component 1 proteins coupled very poorly with the 'wrong' component 2. Rc1(Fe), if complemented with Rc2(Mo), showed only 10-15% of the maximally possible activity. Cross-reaction experiments with isolated polyclonal antibodies revealed that Rc1(Fe) and Rc1(Mo) are immunologically not related. The most active Rc1(Fe) samples appeared to be EPR-silent in the Na2S2O4-reduced state. However, on partial oxidation with K-3[(CN)(6)] or thionine several signals occurred. The most significant signal appears to be the one at g = 2.27 and 2.06 which deviates from all signals so far described for P clusters. It is a transient signal that appears and disappears reversibly in a redox potential region between -100 mV and +150 mV. Another novel EPR signal (g = 1.96, 1.92, 1.77) occurred on further reduction of Rc1(Fe) by using turnover conditions in the presence of a substrate (N-2, C2H2, H+)