The allosteric modulation of complement C5 by knob domain peptides.
Bovines have evolved a subset of antibodies with ultra-long heavy chain complementarity determining regions that harbour cysteine-rich knob domains. To produce high-affinity peptides, we previously isolated autonomous 3-6 kDa knob domains from bovine antibodies. Here, we show that binding of four knob domain peptides elicits a range of effects on the clinically validated drug target complement C5. Allosteric mechanisms predominated, with one peptide selectively inhibiting C5 cleavage by the alternative pathway C5 convertase, revealing a targetable mechanistic difference between the classical and alternative pathway C5 convertases. Taking a hybrid biophysical approach, we present C5-knob domain co-crystal structures and, by solution methods, observed allosteric effects propagating >50 Å from the binding sites. This study expands the therapeutic scope of C5, presents new inhibitors, and introduces knob domains as new, low molecular weight antibody fragments, with therapeutic potential.
['Macpherson|Alex|A|0000-0002-4508-5322', 'Laabei|Maisem|M|0000-0002-8425-3704', 'Ahdash|Zainab|Z|0000-0002-4495-8689', 'Graewert|Melissa A|MA|', 'Birtley|James R|JR|', 'Schulze|Monika-Sarah Ed|ME|', 'Crennell|Susan|S|', 'Robinson|Sarah A|SA|', 'Holmes|Ben|B|', 'Oleinikovas|Vladas|V|', 'Nilsson|Per H|PH|', 'Snowden|James|J|0000-0003-4855-7329', 'Ellis|Victoria|V|', 'Mollnes|Tom Eirik|TE|', 'Deane|Charlotte M|CM|', 'Svergun|Dmitri|D|', 'Lawson|Alastair Dg|AD|', 'van den Elsen|Jean Mh|JM|0000-0002-0367-1956']
D000494:Allosteric Regulation D000818:Animals D002417:Cattle D003182:Complement C5 D055808:Drug Discovery D062105:Molecular Docking Simulation D010455:Peptides D011487:Protein Conformation
complement C5 bovine immunoglobulin human immunology inflammation knob-domain peptides molecular biophysics structural biology