5 word puzzle

[gmgm]

Here's another puzzle that I haven't solved yet. Instructions are the same as with the previous puzzles I posted, read them here: Again, the answer we are looking for should be in the form of one letter, either upper case or lower case.

QUOTE
TRUE
NURSE
SPUR
SLIM

Any suggestions, ideas, thoughts, narrowing of possible answers would be very welcome!

[gmgm]

I'll share with you what I've noticed.

Words seem to reuse three of the letters that occur in the word preceding them. The exception is the last word, which reuses only one (S). All the letters that occur more than once are reused in this way in multiple sequential words. This is all I have found for now and I don't know what to look for next.

[DeGe]

Going further on gmgm's thinking, all words except SLIM use a "U". SLIM should in fact have been SLUM. So i would pick "I" as the answer