The ctpA gene encodes the C-terminal processing protease for the D1 protein of the photosystem II reaction center complex.

The D1 protein of the photosystem II (PSII) complex in the thylakoid membrane of oxygenic photosynthetic organisms is synthesized as a precursor polypeptide (pD1) with a C-terminal extension. Posttranslational processing of the pD1 protein is essential to establish water oxidation activity of the PSII complex. We have recently identified a gene, ctpA, a mutation in which resulted in a loss of PSII activity in the cyanobacterium Synechocystis sp. PCC 6803. To study the function of the CtpA protein, we inactivated the ctpA gene by inserting a kanamycin-resistance gene into its coding sequence. The resultant mutant strain, T564, had no PSII-mediated water oxidation activity, but it had normal cytochrome b6f and photosystem I activities. Measurements of thermoluminescence profiles and rates of reduction of 2,6-dichlorophenolindophenol indicated that PSII complexes in the mutant cells had functional reaction centers that were unable to accept electrons from water. Immunoblot analysis showed that D1, D2, CP47, CP43, and the alpha subunit of cytochrome b559, five integral membrane proteins of PSII, were present in T564 cells. Interestingly, the D1 protein in the mutant cells was 2 kDa larger than that in wild-type cells, due to the presence of a C-terminal extension. We conclude that the CtpA protein is a processing enzyme that cleaves off the C-terminal extension of the D1 protein. Interestingly, the CtpA protein shows significant sequence similarity to the interphotoreceptor retinoid-binding proteins in the bovine, human, and insect eye systems.     

Isolated foveal hypoplasia with secondary nystagmus and low vision is associated with a homozygous SLC38A8 mutation

Foveal hypoplasia, always accompanied by nystagmus, is found as part of the clinical spectrum of various eye disorders such as aniridia, albinism and achromatopsia. However, the molecular basis of isolated autosomal recessive foveal hypoplasia is yet unknown. Individuals of apparently unrelated non consanguineous Israeli families of Jewish Indian (Mumbai) ancestry presented with isolated foveal hypoplasia associated with congenital nystagmus and reduced visual acuity. Genome-wide homozygosity mapping followed by fine mapping defined a 830 Kb disease-associated locus (LOD score 3.5). Whole-exome sequencing identified a single missense mutation in the homozygosity region: c.95T>G, p.(Ile32Ser), in a conserved amino acid within the first predicted transmembrane domain of SLC38A8. The mutation fully segregated with the disease-associated phenotype, demonstrating an ∼10% carrier rate in Mumbai Jews. SLC38A8 encodes a putative sodium-dependent amino-acid/proton antiporter, which we showed to be expressed solely in the eye. Thus, a homozygous SLC38A8 mutation likely underlies isolated foveal hypoplasia.     

Evaluating reliability of ultra-short ECG indices of heart rate variability in diabetes mellitus patients

Our aim was to investigate the reliability of ultra-short HRV in patients with DM. A good correlation was found between the 1 minute and 5 minute parameters for maximal-RR, minimal-RR, average-RR, SDNN, RMSSD, pNN50, and total power. Also, a good correlation between 10 second and 5 minute parameters was found for maximal-RR, minimal-RR, average-RR, and RMSSD. We suggest that certain ultra-short HRV parameters can be used efficiently in DM patients for autonomic evaluation.     

Case for staged thyroidectomy

Recent modifications in the management of well‐differentiated thyroid cancer have resulted in significant alterations in clinical approach. Utilizing a series of preoperative and postoperative risk factors involving both the patient and the disease pathology, we offer the term “staged thyroidectomy” to help organize these risk factors for patients and the endocrine team to optimize management. This approach is intended to incorporate our latest nuanced understanding of certain endocrine pathology and may serve to optimize patient outcomes.