Secondary structure of a complement control protein module by two-dimensional 1H NMR.
The complement control protein (CCP) module (also known as the short consensus repeat) is a consensus sequence of about 60 amino acid residues which is thought to fold independently. It occurs over 140 times in more than 20 extracellular mosaic proteins including 12 proteins of the complement cascade. An isolated CCP module, the 16th repeat from human complement factor H, has been expressed in a yeast vector and shown to fold with the same pattern of disulfide bond formation as is seen in the native protein. Two-dimensional 600-MHz 1H NMR spectra of this module have been recorded at pH 3.3 and 6.0 and analyzed to permit determination of secondary structure in solution. The CCP module comprises two predominantly extended segments (Glu1-His13 and Ala17-Glu27), two segments of double-stranded antiparallel beta-sheet (Gly14-Val16 paired with Tyr31-Cys33 and Gly38-Asp40 paired with Ser57-Ile59), and a short piece of triple-stranded beta-sheet (Glu27-Thr30, Ile44-Leu48, and Lys51-Ser53). Turns occur at Asp22, Gly36, and Glu50, while Gly41-Ala43 appear to form a looped-out segment or bulge. This structure is compared with a secondary structure prediction made on the basis of an alignment scheme of 101 sequences for CCP modules [Perkins, S. J., Haris, P. I., Sim, R. B., & Chapman, D. (1988) Biochemistry 27, 4004-4012]--the experimentally determined secondary structure bears an overall resemblance to the predicted one but differs in the number and position of turns. Some of those amino acid residues which are highly conserved throughout the range of CCP modules appear to play a role in stabilizing the global fold.
Barlow
P N
PN
Department of Biochemistry, University of Oxford, U.K.
Baron
M
M
Norman
D G
DG
Day
A J
AJ
Willis
A C
AC
Sim
R B
RB
Campbell
I D
ID
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003180:Complement C3b Inactivator Proteins / Q000737:chemistry* / Q000235:genetics; D017242:Complement Factor H; D003165:Complement System Proteins / Q000235:genetics*; D016384:Consensus Sequence; D006801:Humans; D006859:Hydrogen; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011506:Proteins / Q000235:genetics*; D015003:Yeasts / Q000235:genetics
C493495:CFH protein, human; D003180:Complement C3b Inactivator Proteins; D011506:Proteins; D006859:Hydrogen; D017242:Complement Factor H; D003165:Complement System Proteins