Submitted January 13, 2006
Accepted May 3, 2006
Analysis of fibrinogen variants at 
387Ile shows
that side-chain of 387 and the tertiary
structure of C terminal tail are important for
not only assembly and secretion of fibrinogen but also
lateral aggregation of protofibrils and XIIIa-catalyzed - dimer formation
Satomi Kani, Fumiko Terasawa, Kazuyoshi Yamauchi, Minoru Tozuka, and Nobuo Okumura*
School of Health Sciences, Shinshu University, Matsumoto, Japan
Shinshu University Hospital, Matsumoto, Japan
The University of Tokyo Hospital, Tokyo, Japan
* Corresponding author; email: nobuoku{at}gipac.shinshu-u.ac.jp.
To examine the role of fibrinogen 
-chain residue
387Ile in the assembly and secretion of this multichain
protein, we synthesized a series of variants with
substitution at 387 by Arg, Leu, Met, Ala or
Asp. Only the variant 387Asp showed impaired
synthesis in the cells and very low secretion into the
medium. In addition, we performed thrombin-catalyzed
fibrin polymerization and factor(F)XIIIa-catalyzed
crosslinking of the -chain for 4 variants. The
degree of lateral aggregation of protofibrils into
fibrin fibers was slightly reduced for 387Arg
and Ala, and moderately reduced for 387Leu and
Met. Although the FXIIIa-catalyzed crosslinking for all
of the variants was slower than that for 387Ile,
that of 387Arg was much more markedly impaired
than that of the others. In summary, our studies
demonstrated that the specific residue at 387
and/or the conformation of 388-411 residues, but
not the length of the C-tail, are critical for
fibrinogen assembly and subsequent secretion. Moreover,
this residue and/or the conformation are also important
for not only the lateral aggregation of fibrin polymers
but also the FXIIIa-catalyzed crosslinking of the &
[gamma]-chain. Interestingly, our results clearly
indicate that the conformations critical for these two
functions are different from each other.
