PDBsum entry: 1kiv

Kringle

PDB id: 1kiv

Contents

Protein chain

78 a.a. *

Waters ×67

* Residue conservation analysis

PDB id:

1kiv

Name:

Kringle

Title:

Recombinant kringle iv-10/m66 variant of human apolipoprotein(a)

Structure:

Apolipoprotein a. Chain: a. Fragment: kringle iv-10. Engineered: yes. Other_details: kiv-10/m66 variant of human apolipoprotein(a)

Source:

Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

2.10Å R-factor: 0.178

Authors:

I.Mochalkin,A.Tulinsky,A.Scanu

Key ref:

I.Mochalkin et al. (1999). Recombinant kringle IV-10 modules of human apolipoprotein(a): structure, ligand binding modes, and biological relevance. Biochemistry, 38, 1990-1998. PubMed id: 10026282 DOI: 10.1021/bi9820558

Date:

26-Aug-98 Release date: 18-May-99

Protein chain

P08519  (APOA_HUMAN) -  Apolipoprotein(a)

Seq: 4548 a.a.

Struc: 78 a.a.

DOI no: 10.1021/bi9820558

Biochemistry 38:1990-1998 (1999)

PubMed id: 10026282

Recombinant kringle IV-10 modules of human apolipoprotein(a): structure, ligand binding modes, and biological relevance.

I.Mochalkin, B.Cheng, O.Klezovitch, A.M.Scanu, A.Tulinsky.

ABSTRACT

are highly homologous with kringle 4 of plasminogen (75-94%) and like the latter are autonomous structural and functional units. Apo(a) contains 14-37 kringle 4 (KIV) repeats distributed into 10 classes (1-10). Lp(a) binds lysine-Sepharose via a lysine binding site (LBS) located in KIV-10 (88% homology with plasminogen K4). However, the W72R substitution that occurs in rhesus monkeys and occasionally in humans leads to impaired lysine binding capacity of KIV-10 and Lp(a). The foregoing has been investigated by determining the structures of KIV-10/M66 (M66 variant) in its unliganded and ligand [epsilon-aminocaproic acid bound modes and the structure of recombinant KIV-10/M66R72 (the W72R mutant). In addition, the EACA liganded structure of a sequence polymorph (M66T in about 42-50% of the human population) was reexamined (KIV-10/T66/EACA). The KIV-10/M66, KIV-10/M66/EACA, and KIV-10/T66/EACA molecular structures are highly isostructural, indicating that the LBS of the kringles is preformed anticipating ligand binding. A displacement of three water molecules from the EACA binding groove and a movement of R35 bringing the guanidinium group close to the carboxylate of EACA to assist R71 in stabilizing the anionic group of the ligand are the only changes accompanying ligand binding. Both EACA structures were in the embedded binding mode utilizing all three binding centers (anionic, hydrophobic, cationic) like plasminogen kringles 1 and 4. The KIV-10/T66/EACA structure determined in this work differs from one previously reported [Mikol, V., Lo Grasso, P. V. and, Boettcher, B. R. (1996) J. Mol. Biol. 256, 751-761], which crystallized in a different crystal system and displayed an unbound binding mode, where only the amino group of EACA interacted with the anionic center of the LBS. The remainder of the ligand extended into solvent perpendicular to the kringle surface, leaving the hydrophobic pocket and the cationic center of the LBS unoccupied. The structure of recombinant KIV-10/M66R72 shows that R72 extends along the ligand binding groove parallel to the expected position of EACA toward the anionic center (D55/D57) and makes a salt bridge with D57. Thus, the R72 side chain mimics ligand binding, and loss of binding ability is the result of steric blockage of the LBS by R72 physically occupying part of the site. The rhesus monkey lysine binding impairment is compared with that of chimpanzee where KIV-10 has been shown to have a D57N mutation instead.