Anti-C4B monoclonal antibody, clone FQS22352

The multiprotein complex C1 initiates the classical pathway of complement activation on binding to antibody-antigen complexes, pathogen surfaces, apoptotic cells, and polyanionic structures. It is formed from the recognition subcomponent C1q and a tetramer of proteases C1r(2)C1s(2) as a Ca2+-dependent complex. Here we have determined the structure of a complex between the CUB1-EGF-CUB2 fragments of C1r and C1s to reveal the C1r-C1s interaction that forms the core of C1. Both fragments are L-shaped and interlock to form a compact antiparallel heterodimer with a Ca2+ from each subcomponent at the interface. Contacts, involving all three domains of each protease, are more extensive than those of C1r or C1s homodimers, explaining why heterocomplexes form preferentially. The available structural and biophysical data support a model of C1r(2)C1s(2) in which two C1r-C1s dimers are linked via the catalytic domains of C1r. They are incompatible with a recent model in which the N-terminal domains of C1r and C1s form a fixed tetramer. On binding to C1q, the proteases become more compact, with the C1r-C1s dimers at the center and the six collagenous stems of C1q arranged around the perimeter. Activation is likely driven by separation of the C1r-C1s dimer pairs when C1q binds to a surface. Considerable flexibility in C1s likely facilitates C1 complex formation, activation of C1s by C1r, and binding and activation of downstream substrates C4 and C4b-bound C2 to initiate the reaction cascade.

Background and aim: Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is a common autosomal recessive disorder. Our objective was to identify the 21-hydroxylase active gene, CYP21A2 mutations in Malaysian 21-OHD patients using different techniques. Materials and methods: Blood samples were obtained from 97 Malaysian 21-OHD patients, which included 40 siblings from 19 families. We used various techniques which include restriction enzyme digestion, Southern blot, multiple ligation-dependent probe amplification (MLPA) and sequencing to elucidate CYP21A2 mutations. Results: Homozygous and compound heterozygous mutations were identified in 95 of the 97 patients (98%). Deletions of CYP21A2 were found in 43 patients (44.3%). Deletions identified in CYP21A2 gene were the usual 30-kb deletion comprising 3'UTR CYP21A1P, C4B and 5'CYP21A2, complete deletion of CYP21A2 gene, deletion in exons 1-3, exons 1-6 and exons 1-8 of CYP21A2. The common mutations identified in CYP21A2 gene were deletion/conversion (22.6%), p.R356W (22%), IVS2-13A/C>G (21.3%), p.I172N (5.3%), p.Q318X (5.3%), and p.P30L (1.03%). This is the first report of the mutation frequency in CYP21A2 gene among the Malay ethnic group. Two novel mutations, c.Y97insT and p.L345P were identified in our patients. Our results show good phenotype-genotype correlation in most of the cases, although clinical variations were identified in some patients. Conclusions: The study has found various mutations including deletions in CYP21A2 gene in Malaysian patients with 21-hydroxylase deficiency using the MLPA technique that is being widely used in present laboratory settings. (C) 2013, Editrice Kurtis