Question about signal cleavage site 
of SDHA flavoprotein:
N-term sequencing of bovine FP gave 1-SAKVSDA. 
Numbering like this, the flavin-binding histidine is H56 :
 Birch-Machin, M. A., Farnsworth, L., Ackrell, B. A., 
 Cochran, B., Jackson, S., Bindoff, L. A., Aitken, A., 
 Diamond, A. G. & Turnbull, D. M. (1992).
 The sequence of the flavoprotein subunit of bovine heart 
 succinate dehydrogenase.  J Biol Chem 267, 11553-8.

However for the porcine FP the N-term sequence is SSAKV.
This makes the Flavin-ligand H57, and all other numbers advanced 1 also:
 Huo, X., Su, D., Wang, A., Zhai, Y., Xu, J., Li, X., Bartlam, M., 
 Sun, F. & Rao, Z. (2007). Preliminary molecular characterization 
 and crystallization of mitochondrial respiratory complex II 
 from porcine heart. Febs J 274, 1524-9.

(The latter cutting point was confirmed for human FP by mass spec,
but I don't remember the reference.)