PMID- 10631976
OWN - NLM
STAT- MEDLINE
DCOM- 20000214
LR  - 20181113
IS  - 0961-8368 (Print)
IS  - 1469-896X (Electronic)
IS  - 0961-8368 (Linking)
VI  - 8
IP  - 12
DP  - 1999 Dec
TI  - Alpha1-microglobulin chromophores are located to three lysine residues semiburied 
      in the lipocalin pocket and associated with a novel lipophilic compound.
PG  - 2611-20
AB  - Alpha1-microglobulin (alpha1m) is an electrophoretically heterogeneous plasma 
      protein. It belongs to the lipocalin superfamily, a group of proteins with a 
      three-dimensional (3D) structure that forms an internal hydrophobic 
      ligand-binding pocket. Alpha1m carries a covalently linked unidentified 
      chromophore that gives the protein a characteristic brown color and extremely 
      heterogeneous optical properties. Twenty-one different colored tryptic peptides 
      corresponding to residues 88-94, 118-121, and 122-134 of human alpha1m were 
      purified. In these peptides, the side chains of Lys92, Lys118, and Lys130 carried 
      size heterogeneous, covalently attached, unidentified chromophores with molecular 
      masses between 122 and 282 atomic mass units (amu). In addition, a previously 
      unknown uncolored lipophilic 282 amu compound was found strongly, but 
      noncovalently associated with the colored peptides. Uncolored tryptic peptides 
      containing the same Lys residues were also purified. These peptides did not carry 
      any additional mass (i.e., chromophore) suggesting that only a fraction of the 
      Lys92, Lys118, and Lys130 are modified. The results can explain the size, charge, 
      and optical heterogeneity of alpha1m. A 3D model of alpha1m, based on the 
      structure of rat epididymal retinoic acid-binding protein (ERABP), suggests that 
      Lys92, Lys118, and Lys130 are semiburied near the entrance of the lipocalin 
      pocket. This was supported by the fluorescence spectra of alpha1m under native 
      and denatured conditions, which indicated that the chromophores are buried, or 
      semiburied, in the interior of the protein. In human plasma, approximately 50% of 
      alpha1m is complex bound to IgA. Only the free alpha1m carried colored groups, 
      whereas alpha1m linked to IgA was uncolored.
FAU - Berggard, T
AU  - Berggard T
AD  - Department of Cell and Molecular Biology, Lund University, Sweden.
FAU - Cohen, A
AU  - Cohen A
FAU - Persson, P
AU  - Persson P
FAU - Lindqvist, A
AU  - Lindqvist A
FAU - Cedervall, T
AU  - Cedervall T
FAU - Silow, M
AU  - Silow M
FAU - Thogersen, I B
AU  - Thogersen IB
FAU - Jonsson, J A
AU  - Jonsson JA
FAU - Enghild, J J
AU  - Enghild JJ
FAU - Akerstrom, B
AU  - Akerstrom B
LA  - eng
GR  - HL49542/HL/NHLBI NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Protein Sci
JT  - Protein science : a publication of the Protein Society
JID - 9211750
RN  - 0 (Glycoproteins)
RN  - 0 (Immunoglobulin A)
RN  - 0 (Membrane Glycoproteins)
RN  - 0 (Peptide Fragments)
RN  - 0 (SPINT2 protein, human)
RN  - 9088-41-9 (Trypsin Inhibitor, Kunitz Soybean)
RN  - K3Z4F929H6 (Lysine)
SB  - IM
MH  - Animals
MH  - Chromatography, High Pressure Liquid
MH  - Color
MH  - Glycoproteins/*chemistry/immunology/isolation & purification
MH  - Humans
MH  - Immunoglobulin A/chemistry
MH  - Lysine/*chemistry
MH  - Mass Spectrometry
MH  - *Membrane Glycoproteins
MH  - Mice
MH  - Models, Molecular
MH  - Peptide Fragments/chemistry
MH  - Peptide Mapping
MH  - Rats
MH  - Sequence Alignment
MH  - Sequence Analysis, Protein
MH  - Spectrometry, Fluorescence
MH  - *Trypsin Inhibitor, Kunitz Soybean
PMC - PMC2144230
EDAT- 2000/01/13 09:00
MHDA- 2000/02/19 09:00
CRDT- 2000/01/13 09:00
PHST- 2000/01/13 09:00 [pubmed]
PHST- 2000/02/19 09:00 [medline]
PHST- 2000/01/13 09:00 [entrez]
AID - 10.1110/ps.8.12.2611 [doi]
PST - ppublish
SO  - Protein Sci. 1999 Dec;8(12):2611-20. doi: 10.1110/ps.8.12.2611.