Crystallization and molecular-replacement solution of a diagnostic fluorescent dye in complex with a specific Fab fragment.
Tetrasulfocyanine (TSC) has been described as a fluorescent probe for tumour imaging. The complex of TSC and the Fab antibody fragment MOR03268 has been crystallized in three different crystal forms. MOR03268 was identified from the HuCAL GOLD library and further optimized to bind TSC with high affinity (Kd = 0.6 nM). For two of the three crystal forms (forms 1 and 2), data sets could be collected to 2.8 and 2.85 A resolution, respectively. Form 1 belongs to space group I222, with unit-cell parameters a = 72, b = 99, c = 154 A. Form 2 belongs to space group P4(3)2(1)2, with unit-cell parameters a = b = 77, c = 379 A. Form 3 only diffracted to 8 A and was not analyzed further. Molecular-replacement solutions for forms 1 and 2 were found and rebuilding and refinement is in progress. Form 1 contains one Fab molecule per asymmetric unit, while form 2 harbours two. Judging from the green colour of the crystals, both forms contain the Fab molecule bound to the green TSC dye and in both the hydrolysis-sensitive dye molecule is protected from degradation for several weeks to months. The structures should reveal the molecular basis of the high-affinity recognition of TSC by the Fab molecule MOR03268.
Hillig
Roman C
RC
Bayer Schering Pharma AG, Research Laboratories, D-13342 Berlin, Germany. roman.hillig@schering.de
Baesler
Siegfried
S
Urlinger
Stefanie
S
Stark
Yvonne
Y
Bauer
Susanne
S
Badock
Volker
V
Huber
Martina
M
Bahr
Inke
I
Schirner
Michael
M
Licha
Kai
K
D000595:Amino Acid Sequence; D001666:Binding Sites, Antibody; D003460:Crystallization; D005456:Fluorescent Dyes / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007211:Indoles / Q000138:chemical synthesis / Q000378:metabolism; D008969:Molecular Sequence Data; D012996:Solutions / Q000737:chemistry
D005456:Fluorescent Dyes; D007140:Immunoglobulin Fab Fragments; D007211:Indoles; D012996:Solutions; C028418:tetrasulfophthalocyanine