TABLE 1.
Effect of C1 assembly on the solvent accessibility of the lysine residues of C1r
Residues showing significant changes in their accessibility are shown in bold type.
| Domain | C1r protein |
|||
|---|---|---|---|---|
| Lysines | SASAa | Mann-Whitney U test, H0b, p < 0.01c | Accessibility within C1 | |
| Å2 | ||||
| CUB1 | K7 | –d | False | Decreased |
| K19 | –d | True | Unchanged | |
| K40 | –d | True | Unchanged | |
| K60 | –d | True | Unchanged | |
| K65 | –d | True | Unchanged | |
| K66 | –d | True | Unchanged | |
| K85 | –d | NDe | ND | |
| K86 | –d | ND | ND | |
| K94 | –d | True | Unchanged | |
| K115 | –d | True | Unchanged | |
| EGF | K134 | 59.0 | ND | ND |
| CUB2 | K218 | –d | True | Unchanged |
| K245 | –d | True | Unchanged | |
| K253 | –d | True | Unchanged | |
| K282 | –d | ND | ND | |
| CCP1 | K291f | 81.2 | True & false | Unchanged & decreasedf |
| K296f | 159.0 | |||
| K322 | 99.8 | ND | ND | |
| K355 | 101.1 | True | Unchanged | |
| CCP2 | K357 | 46.7 | True | Unchanged |
| K382 | 114.3 | False | Decreased | |
| K395 | 145.6 | False | Decreased | |
| K419 | 64.0 | ND | ND | |
| K423 | 50.6 | ND | ND | |
| K426 | 165.6 | ND | ND | |
| a.p.g | K436 | 89.3 | ND | ND |
| SP | K452 | 124.4 | False | Decreased |
| K454 | 136.1 | False | Decreased | |
| K490 | 8.8 | ND | ND | |
| K514 | 42.4 | ND | ND | |
| K585 | 101.0 | True | Unchanged | |
| K610 | 85.3 | ND | ND | |
| K629 | 115.2 | True | Unchanged | |
| K672 | 30.0 | True | Unchanged | |
| K681 | 98.9 | True | Unchanged | |
| K682 | 146.4 | True | Unchanged | |
a Solvent accessibility surface area of lysine side chains. Accessible surface areas of C1r are based on available X-ray data (pdb accession numbers: 1APQ (EGF), 1GPZ (CCP1-CCP2-SP), and 1MD8 (SP)) and calculated by using the software program VADAR (44).
b H0, hypothesis of “no difference” of solvent accessibility between the free tetramer and C1.
c Two-sided p value; the significant level at which H0 is rejected is set to 1%.
d No structure available.
e ND, not determined.
f Residues covered by two distinct peptic peptides with different solvent accessibility modifications upon C1q binding.
g Activation peptide.
h Residue was undefined in the crystal structure (10).