Identification and analysis of a novel mutation in PEPD gene in two Kashmiri siblings with prolidase enzyme deficiency

Prolidase deficiency (PD) is a rare inborn disorder of collagen metabolism characterized by chronic recurrent cutaneous ulceration. We report a novel 3 bp insertion in the 12th exon of the PEPD gene in two Kashmiri siblings with prolidase deficiency phenotype. This mutation results in addition of an extra alanine residue at the amino-acid position number 304 of prolidase peptide. The structural analysis showed that this Ala insertion is located at the helix (a.a. 300–320), which contains several important hydrogen bonds between residues essential for structural folding for the enzyme activity. In silico analysis suggests that this insertion mutation might distort or bend the helical feature to affect the hydrogen-bond network between residues of neighboring secondary structures and deform the metal-binding geometry of the enzyme. Although approximately 70 PEPD gene mutations and polymorphisms have been reported in various ethnic groups, we however report, for the first time, the identification of insertion mutation in human the PEPD gene.     

Correlation between the amide proton exchange rates and the denaturation temperatures in globular proteins related to the basic pancreatic trypsin inhibitor.

Nuclear magnetic resonance was used to measure the hydrogen-deuterium exchange rates for individual interior amide protons in a group of small globular proteins related to the basic pancreatic trypsin inhibitor (BPTI). These proteins include two homologous proteins and seven chemical modifications of BPTI. It was previously shown that the spatial structure of BPTI is preserved in all these related proteins. The exchange rates for corresponding amide protons in the different proteins were found to vary by a factor of as much as 5 X 104. The proton exchange is correlated with the thermal stability of the proteins, i.e. the lower the denaturation temperature, the faster the NH exchange. Further evidence that the exchange of interior amide protons is promoted by global fluctuations of the protein structures comes from the observation that the order of the relative exchange rates for the individual protons is the same in all the different species. This is the third in a series of three papers on nuclear magnetic resonance studies of labile protons in BPTI-related proteins. A detailed interpretation of the data will be given in a forthcoming paper.     

Five new records of bee flies (Bombyliidae,Diptera) from Saudi Arabia with zoogeographical remarks

Five bee-fly species (Bombyliidae, Diptera) have been listed in this paper as new to the Kingdom of Saudi Arabia. Four of the recorded species have been identified to the level of species, namely: Bombomyia discoidea (Fabricius, 1794), Spogostylum candidum (Sack, 1909), Exoprosopa linearis Bezzi, 1924, and Exoprosopa minos (Meigen, 1804), while the fifth one only to genus, Desmatoneura sp. The species have been collected from Al-Baha and Asir Provinces in the south-western part of the Kingdom. One of the four identified species, Exoprosopa linearis, has an Afrotropical affinity, and another two, Spogostylum candidum and Bombomyia discoidea, have considerable Afrotropical distributions, and this result agrees to some extent with studies considering these parts of the Arabian Peninsula, including Al-Baha and Asir Provinces, having Afrotropical influences and may be included in the Afrotropical Region rather than in the Palaearctic Region or the Eremic zone.