1KXQ

Camelid VHH Domain in Complex with Porcine Pancreatic alpha-Amylase

Summary for 1KXQ

• Entry DOI: 10.2210/pdb1kxq/pdb
• Related: 1kxt 1kxv
• Descriptor: alpha-amylase, pancreatic, antibody VHH fragment CABAMD9, CALCIUM ION, ... (5 entities in total)
• Functional Keywords: alpha 8 beta 8, beta barrel, hydrolase, immune system
• Biological source: Camelus dromedarius (Arabian camel); More
• Cellular location: Secreted, extracellular space: P00690
• Total number of polymer chains: 8
• Total formula weight: 274218.37

Authors

Desmyter, A.,Spinelli, S.,Payan, F.,Lauwereys, M.,Wyns, L.,Muyldermans, S.,Cambillau, C. (deposition date: 2002-02-01, release date: 2002-06-19, Last modification date: 2024-11-06)

Primary citation

Desmyter, A.,Spinelli, S.,Payan, F.,Lauwereys, M.,Wyns, L.,Muyldermans, S.,Cambillau, C.
Three camelid VHH domains in complex with porcine pancreatic alpha-amylase. Inhibition and versatility of binding topology.
J.Biol.Chem., 277:23645-23650, 2002

PubMed Abstract: Camelids produce functional antibodies devoid of light chains and CH1 domains. The antigen-binding fragment of such heavy chain antibodies is therefore comprised in one single domain, the camelid heavy chain antibody VH (VHH). Here we report on the structures of three dromedary VHH domains in complex with porcine pancreatic alpha-amylase. Two VHHs bound outside the catalytic site and did not inhibit or inhibited only partially the amylase activity. The third one, AMD9, interacted with the active site crevice and was a strong amylase inhibitor (K(i) = 10 nm). In contrast with complexes of other proteinaceous amylase inhibitors, amylase kept its native structure. The water-accessible surface areas of VHHs covered by amylase ranged between 850 and 1150 A(2), values similar to or even larger than those observed in the complexes between proteins and classical antibodies. These values could certainly be reached because a surprisingly high extent of framework residues are involved in the interactions of VHHs with amylase. The framework residues that participate in the antigen recognition represented 25-40% of the buried surface. The inhibitory interaction of AMD9 involved mainly its complementarity-determining region (CDR) 2 loop, whereas the CDR3 loop was small and certainly did not protrude as it does in cAb-Lys3, a VHH-inhibiting lysozyme. AMD9 inhibited amylase, although it was outside the direct reach of the catalytic residues; therefore it is to be expected that inhibiting VHHs might also be elicited against proteases. These results illustrate the versatility and efficiency of VHH domains as protein binders and enzyme inhibitors and are arguments in favor of their use as drugs against diabetes.

PubMed: 11960990
DOI: 10.1074/jbc.M202327200

Experimental method

X-RAY DIFFRACTION (1.6 Å)