APOSTREPTAVIDIN, PH 3.32, SPACE GROUP I222

Binding of biotin to streptavidin stabilizes intersubunit salt bridges between Asp61 and His87 at low pH.

In Crystals of Complexes of Streptavidin with Peptide Ligands Containing the Hpq Sequence the Pka of the Peptide Histidine is Less Than 3.0

Structure-Based Design Tools: Structural and Thermodynamic Comparison with Biotin of a Small Molecule that Binds Streptavidin with Micromolar Affinity

Preparation of a Protein-Dimerizing Ligand by Topochemistry and Structure-Based Design

Topochemical Catalysis Achieved by Structure-Based Ligand Design

Topochemistry for Preparing Ligands that Dimerize Receptors

Binding to Protein Targets of Peptidic Leads Discovered by Phage Display: Crystal Structures of Streptavidin-Bound Linear and Cyclic Peptide Ligands Containing the Hpq Sequence

Structure-Based Design of High Affinity Streptavidin Binding Cyclic Peptide Ligands Containing Thioether Cross-Links

DPSKDSKAQVSAAEAGITGTWYNQLGSTFIVTAGADGALTGTYESAVGNAESRYVLTGRYDSAPATDGSGTALGWTVAWK
NNYRNAHSATTWSGQYVGGAEARINTQWLLTSGTTEANAWKSTLVGHDTFTKVKP

REJECTION CRITERIA: (I(H)I - <I(H)I>) > [0.30 * (<GLOBAL I>) + 0.10*I(H)I], WHERE I(H)I IS THE ITH OBSERVATION OF THE INTENSITY OF REFLECTION H (M.G.ROSSMANN, A.G.W.LESLIE, S.S.ABDEL-MEGUID, T.TSUKIHARA, J.APPL.CRYST. 12, 570 - 581). THIS REJECTION CRITERION IS THE DEFAULT OF THE MSC PROGRAM BIOTEX.

SYNTHETIC MOTHER LIQUOR OF 75% SATURATED AMMONIUM SULFATE, 25% 1.0 M POTASSIUM ACETATE ADJUSTED TO PH 3.32.

THE FOLLOWING ATOMS HAD WEAK DENSITY AND OCCUPANCIES WERE
REFINED:
ALA B 13
GLU B 14
ALA B 15
GLU B 51 (CG, HG1, HG2, CD, OE1, OE2)
ARG B 53 (NE, HE, CZ, NH1, HH11, HH12, NH2, HH21, HH22)
ARG B 84 (NE, HE, CZ, NH1, HH11, HH12, NH2, HH21, HH22)
GLY B 98
GLY B 99
ALA B 100
GLU B 101
ALA B 102
ARG B 103 (NE, HE, CZ, NH1, HH11, HH12, NH2, HH21, HH22)
GLU B 116 (CG, HG1, HG2, CD, OE1, OE2)
LYS B 134
PRO B 135
ALA D 13
GLU D 14
ALA D 15
ASP D 36 (CG, OD1, OD2)
ARG D 53 (NE, HE, CZ, NH1, HH11, HH12, NH2, HH21, HH22)
ASN D 82 (CG, OD1, ND2, HD21, HD22)
ARG D 84 (NE, HE, CZ, NH1, HH11, HH12, NH2, HH21, HH22)
ALA D 100
GLU D 101 (CB, HB1, HB2, CG, HG1, HG2, CD, OE1, OE2)
ARG D 103 (NE, HE, CZ, NH1, HH11, HH12, NH2, HH21, HH22)
GLU D 116 (CG, HG1, HG2, CD, OE1, OE2)
VAL D 133

RESIDUES TYR B 60 THROUGH SER B 69 AND TYR D 60 THROUGH
SER D 69 WERE REFINED IN TWO CONFORMATIONS BECAUSE UPON
PROTONATION OF ASP 61 AT LOW PH, ASP 61 UNDERGOES A LARGE
SHIFT IN CONFORMATION AND CHANGE IN HYDROGEN BONDING. THE
LOOPS COMPRISING RESIDUES ASP B 61 THROUGH SER B 69 AND
ASP D 61 THROUGH SER D 69 ALSO UNDERGO CORRESPONDING
CONFORMATIONAL CHANGES. HOWEVER SOME OF THESE RESIDUES ARE
DISORDERED AND NOT VISIBLE IN EITHER CONFORMATION.

TYR B 22 IS DISORDERED BETWEEN 2 CONFORMATIONS ONE OF WHICH
OCCUPIES A SIMILAR REGION OF SPACE AS A 2-FOLD RELATED
B 22. PROPER REFINEMENT WITH XPLOR IS NOT POSSIBLE BECAUSE
OF THE OVERLAP OF ONE CONFORMER WITH THE SYMMETRY RELATED
COUNTERPART. THE FOLLOWING WATERS WERE USED TO ACCOUNT FOR
DENSITY DUE TO THIS CONFORMER OF TYR B 22: HOH 491,
HOH 1460. NO HYDROGENS ARE INCLUDED FOR THESE "WATERS".

BIOTIN-BINDING PROTEIN, APOSTREPTAVIDIN, PH 3.32

MRKIVVAAIAVSLTTVSITASASADPSKDSKAQVSAAEAGITGTWYNQLGSTFIVTAGADGALTGTYESAVGNAESRYVL
TGRYDSAPATDGSGTALGWTVAWKNNYRNAHSATTWSGQYVGGAEARINTQWLLTSGTTEANAWKSTLVGHDTFTKVKPS
AASIDAAKKAGVNNGNPLDAVQQ