Serum Amyloid P Component (SAP), a putative molecular chaperone, is a homopentameric plasma protein of 25kDa subunits. It binds to the amyloid fibrils of misfolded proteins, which cause amyloidosis in humans. SAP not only stabilizes amyloid fibrils but also protects them from proteolytic and cell mediated degradation. SAP has been co-crystallized with three different aminoalkyl phosphonates that bind at the amyloid recognition site of SAP, and the X-ray crystal structures were determined at atomic resolution. A secondary aim of this work was to understand the enhanced amyloidogenic potential of L55P and V30M transthyretin (TTR) protein. TTR misfolding has been implicated in number of human diseases such as senile systemic amyloidosis, familial amyloid polyneuropathy and familial amyloid cardiopathy. TTR protein is a thyroxine binding protein (14kDa) existing as a tetramer in vivo. L55P and V30M mutant TTR are the most aggressive and most common mutants, respectively, in causing FAP. L55P and V30M mutant TTR protein were expressed in E.coli and purified using anion-exchange chromatography and gel filtration. L55P and V30M TTR were co-crystallised with MDS84, a compound that has been demonstrated to stabilize the tetramer in vitro. The X-ray structures of L55P and V30M, TTR mutant proteins have been determined at 1.5Å and 2.1Å resolution. In addition, research was carried out on the bacterial protein Burkholderia invasion protein D (BipD). BipD (33kDa) belongs to type III secretion system of Burkholderia pseudomallei. It creates a pore in the host cell membrane to help the B. pseudomallei invasion. This bacterial infection causes melioidosis disease in humans. To determine the ligand recognition site of BipD, its high-resolution crystal structure has been determined at 1.5Å. This high resolution BipD structure is more complete than its previously solved structures and is in the new space group C2. The BipD structure presented in this research may help to design potential chemical inhibitors of BipD to prevent bacterial invasion into human body. The molecular chaperones play an important role in the protein refolding and assembly. ATJ11 is of 14kDa protein belongs to DnaJ co-chaperone family. The protein has been expressed in E.coli and purified by affinity and cation exchange chromatography. The biophysical study of ATJ11 (CD spectrum) has been conducted showing its predominant α-helical structure and attempts were made to crystallise it but no protein crystals have been obtained.

Nystagmus is a disorder of eye movement characterised by irregular, uncontrolled and repetitive eye movements. It can occur in a broad spectrum of clinical situations and diseases or it may occur in isolation and an inherited disorder. Surprisingly little is known about the underlying mechanisms of ocular-motor control. Similarly, the pathophysiological mechanisms underpinning nystagmus is also poorly understood. By studying pedigrees in whom nystagmus seems to be inherited as an isolated trait (Congenital Idiopathic Nystagmus), it may be possible to identify some of the genetic causes of this disorder and subsequently understand the pathophysiology. This thesis describes a molecular genetic study of congenital nystagmus. A clinical phenotyping study is followed by linkage analysis and positional cloning. A novel nystagmus gene is investigated in a large cohort of Congenital Idiopathic Nystagmus (CIN) patients and X-inactivation studies are performed. Subsequently, cell culture and RT-PCR work is performed to study expression of this gene. Additionally a pedigree with an atypical congenital nystagmus disorder is investigated and a new mutation within a known cerebellar disease gene is identified. This work contributed to the identification of the first gene for Congenital Idiopathic Nystagmus (CIN). The first detailed temporal expression study of the FRMD7 nystagmus gene was also performed in this study which has directed further studies into the pathogenesis of CIN. Identification of a new mutation in the CACNA1A gene in a pedigree with nystagmus and subtle cerebellar signs has lead to the consideration of this gene in patients who present to hospital with isolated atypical nystagmus.