Stable plasma membrane expression of the soluble domain of the human insulin receptor in yeast

Substitutions in the conserved C2C domain of otoferlin cause DFNB9, a form of nonsyndromic autosomal recessive deafness

DFNB, the nonsyndromic hearing loss with an autosomal recessive mode of inheritance constitutes the majority of severe to profound prelingual forms of hearing impairment, usually leading to inability of speech acquisition. We analyzed a consanguineous family with autosomal recessive deafness which has been shown to segregate within chromosomal region 2p23.1 (DFNB9; MIM 601071). By SSCP analysis and DNA sequencing of the 48 exons of the DFNB9 gene, coding for otoferlin, previously reported mutations in OTOF were excluded. Next to a frequent T > C single nucleotide polymorphism in exon 8, two novel mutations linked in exon 15 of the OTOF long splice form were identified comprising substitutions at positions 490 (Pro > Gln) and 515 (Ile > Thr), both located in the conserved Ca(2+) binding C2C domain of this peptide. Comparisons of homology using human and mice otoferlins and closely related peptides and computer simulation analyses suggest that changes in the mutated segment's secondary structure affect the Ca(2+) binding capacity of the C2C domain in otoferlin.

The post-genomic era of interactive proteomics: facts and perspectives

The availability of completed genome sequences of several eukaryotic and prokaryotic species has shifted the focus towards the identification and characterization of all gene products that are expressed in a given organism. In order to cope with the huge amounts of data that have been provided by large-scale sequencing projects, high-throughout methodologies also need to be applied in the emerging field of proteomics. In this review, we discuss methods that have been recently developed in order to characterize protein interactions and their functional relevance on a large scale. We then focus on those methodologies that are suitable for the identification and characterization of protein-protein interactions, namely the yeast two-hybrid system and related methods. Several recent studies have demonstrated the power of automated approaches involving the yeast two-hybrid system in building so-called "interaction networks", which hold the promise of identifying the entirety of all interactions that take place between proteins expressed in a certain cell type or organism. We compare the yeast two-hybrid system with several other screening methods that have been developed to investigate interactions between proteins that are not amenable to conventional yeast two-hybrid screenings, such as transcriptional activators and integral membrane proteins. The eventual adaptation of such methods to a high-throughput format and their use in combination with automated yeast two-hybrid screenings will help in elucidating protein-protein interactions on a scale that would have been unthinkable just a few years ago.

Genetic approaches to the identification of interactions between membrane proteins in yeast

The recent sequencing of entire eukaryotic genomes has renewed the interest in identifying and characterizing all gene products that are expressed in a given organism. The characterization of unknown gene products is facilitated by the knowledge of its binding partners. Thus, a novel protein may be classified by identifying previously characterized proteins that interact with it. If such an approach is carried out on a large scale, it may allow the rapid characterization of the thousands of predicted open reading frames identified by recent sequencing projects. Currently, the yeast two-hybrid system is the most widely used genetic assay for the detection of protein-protein interactions. The yeast two-hybrid system has become popular because it requires little individual optimization and because, as compared to conventional biochemical methods, the identification and characterization of protein-protein interactions can be completed in a relatively short time span. In this review, we briefly discuss the yeast two-hybrid system and its application to large scale screening studies that aim at deciphering all protein-protein interactions taking place in a given cell type or organism. We then focus on a class of proteins that is unsuitable for conventional yeast two-hybrid systems, namely integral membrane proteins and membrane-associated proteins, and describe several novel genetic systems that combine the advantages of the yeast two-hybrid system with the potential to identify interaction partners of membrane-associated proteins in their natural setting.