Alex:
Assuming that you are only interested in amino acid-to-amino acid links,
here is a non-exhaustive list of refs to odd x-links (additions welcome!!):
Ser-to-His: Biochemistry (1986) 25: 2392-96 (aka histidinoalanine)
Cys-to-His: JBC (1982) 257: 6414
Trp-to-Trp: Science (1991) 252: 817
Cys-to-Tyr: Nature (1991) 350:87
Cys-to-Trp: Naturwissenschaften (1987) 74: 367-373 (aka tryptathionine,
not cystophan as we called it here before finding it had already been
discovered - !@$%!!)
Lys-to-Tyr: Science (1996) (for some reason I've lost the volume to this
ref, but the page is 1078; author is SF Wang
Then there are a variety of isopeptide (Lys-to-Asp/Asn/Glu/Gln) links which
are known.
Some of the above can be found in Meth Enzymol vols 106&107, see esp 106:
351 (H/S) & 355 (H/C), 107: 241 & 258 (isopeptides links), 377 &388
(dityrosine)
Then, perhaps the most amazing, although mayve not a crosslink in the sense
that the residues are sequentially adjacent, is the one involving the
Ser-Tyr-Gly tripeptide that forms the fluorophore in the central helix of
green fluorescent protein. The whole protein is fascinating as well. The
central helix is surrounded by an 11-stranded beta-barrel (aka "green
lantern structure": B-C Wang's terminology) See Science (1996) 273:1392,
and also a great review article in Ann Rev Biochem (1998) 67:509-44.
Then, there are Lys/Lys ones in connective tissues like lysinorleucine and
desmosine that are covered in textbooks like Stryer.
Also a good one in collagen which ought to be included on this list too -
the crosslink remains after proteolysis and is excreted. This forms the
basis of an apparently highly accurate test for osteoporosis, but I'm
lacking a good ref for that at the moment.
John Hempel, PhD Ph (412) 624 0161
University of Pittsburgh FAX (412) 624 4759
Department of Biological Sciences
Pittsburgh PA 15260 email: hempel@psc.edu
http://www.pitt.edu/~biology/faculty/hempel.html