请问哪个字母最长?

请问哪个字母最长?

脑筋急转弯的话,是smiles,两个s间相距一英里.
真实的,如下：
记得两个月以前我曾经贴过最长的英文单词是“pneumonoultramicroscopicsilicovolcanoconiosis
[医]硅酸盐沉着病,矽肺病”是错误的 ,
据疯狂英语2001,九月,第30期载：
最长的是1,913个字母,
是“色氨酸合成酶A蛋白质”
（一种含有267种氨基酸酶）的全称----
一般的字典上是见不着的.
（你可以翻翻医学专用词汇字典^_*）
单词如下：
Methionylglutaminylarginyltyrosylglutamylserylleucylphenylalanylalany
lglutaminylleucyllysylglutamylarginyllysylglutamylglycylalanylphenyla
lanylvalylprolyphenylalanYlvalythreonylleucylglycylaspartylprolylglyc
ylisoleucylglutamylglutaminylsErylleucyllysylisoleucylaspartylthreony
lleucylIsoleucylglutamylalanylglycylalanylasparthlalanylleucylglutamy
lleucylglycylisoleucylprolylphenylalanylseRylaspartylprolylleucylalan
ylaspartylglycylpRolylthreOnylisoleucylglutaminylasPfraginylalanylthr
eonylleucylarfinylalanylphenylalanylalanylalanylglycylvalythreonylpro
lylalanylglutaminylcysteinylphenylalanylglutamylmethionylleucylalanyl
leuOylisoleucylarginylglutaminyllysyhistidylprolylthreonylisoleucylpr
olylisoleucylglycylleucylmethionyltyrosylalanylasparaginylleucylvalyl
phenylalanylasparaginyllysyglycylisoleucylaspartylglutamylphenylalany
lthrosylalanylglutaminylcysteinylglutamyllysylvalylglycylvalylasparty
lserylvalylleucylvalylalnylaspartylvalylprolylvalylglUtaminylglutamyl
serylalanylprolylphenylalanylarginylglutaminylalanylalanylleucylarginy
lhistidylasparaginyvalylalanylprolylisoleucylprolylisoleucylphenylalan
ylisoleucylphenylalanylisoleucylcysteinylprolylprolylaspartylalanylasp
artylaspartylaspartylleucylleucylarginylglutaminylisoleucylalanylseryl
tyrosylglycylarginylglycyltyrosylthreonyltyrOsylleucylleucylserylargin
ylalanylglycylvalylthreonylglycylalanylglutamYlasparainylarginylalanyl
alanylleucylprolylleucylasparaginylhistidylleucylValylalanyllysylleucy
llysylglutamyltyrosylasparaginylalanylalanylprolylprolylleucylglutaminy
lglgycylphenylalanylglycylisoleucylserylalanylprolylaspartylglutaminylv
alyllysylalanylalanylisoleucylaspartylalanylglycylalanylalanylglycylala
nylisoleucylserylglycylserylalanylisoleucylvalyllysylisoIeucylisoleucyl
glutamylglutaminylHistidylasparaginyliSoleucylglutamylprolylglutamyllys
ylmethionylleucylalanylalanylleucyllysylvalylphenylalanylcalylglutaminy
lprolylmethionlysylalanylalanylthreonylarginylserine