A subgroup of light-driven sodium pumps with an additional Schiff base counterion.

Light-driven sodium pumps (NaRs) are unique ion-transporting microbial rhodopsins. The major group of NaRs is characterized by an NDQ motif and has two aspartic acid residues in the central region essential for sodium transport. Here we identify a subgroup of the NDQ rhodopsins bearing an additional glutamic acid residue in the close vicinity to the retinal Schiff base. We thoroughly characterize a member of this subgroup, namely the protein ErNaR from Erythrobacter sp. HL-111 and show that the additional glutamic acid results in almost complete loss of pH sensitivity for sodium-pumping activity, which is in contrast to previously studied NaRs. ErNaR is capable of transporting sodium efficiently even at acidic pH levels. X-ray crystallography and single particle cryo-electron microscopy reveal that the additional glutamic acid residue mediates the connection between the other two Schiff base counterions and strongly interacts with the aspartic acid of the characteristic NDQ motif. Hence, it reduces its pKa. Our findings shed light on a subgroup of NaRs and might serve as a basis for their rational optimization for optogenetics.

Parsing the components of the psychomotor syndrome in schizophrenia.

OBJECTIVE: Catatonia, extrapyramidal signs, psychomotor slowing, and (motoric) neurological soft signs are well-known psychomotor symptoms in schizophrenia. This study aims at investigating the interrelations between these symptoms. In addition, associations between psychomotor symptoms, clinical symptoms, and cognitive functioning will be studied. METHOD: An extensive test battery containing psychomotor (Bush Francis Catatonia Rating Scale; St Hans Rating Scale; Salpêtrière Retardation Rating Scale; Neurological Evaluation Scale) and clinical (Positive and Negative Syndrome Scale; Calgary Depression Scale) rating scales as well as instrumental psychomotor tests (Line Copying Task; Finger Tapping Task) and cognitive tasks (Symbol Digit Substitution Test; Stroop Colour Word Test; Continuous Performance Test; Letter Number Sequencing) was administered to a sample of 124 patients with schizophrenia or schizoaffective disorder. RESULTS: Correlational analyses showed that two clusters emerge from our data: first, a psychomotor poverty cluster referring to the interrelations between catatonia, parkinsonism, psychomotor slowing, and negative symptoms; second, a cluster containing motoric neurological soft signs, which were found to be correlated with cognitive functioning. CONCLUSION: Psychomotor abnormalities are highly prevalent phenomena in schizophrenia that have to be considered as a heterogeneous construct. However, longitudinal and neurobiological research is needed to further explore the precise nature of the interrelations found in this study.