Structure of the Human Cytomegalovirus Protease Catalytic Domain Reveals a Novel Serine Protease Fold and Catalytic Triad

Abstract

Proteolytic processing of capsid assembly protein precursors by herpesvirus proteases is essential for virion maturation. A 2.5 A crystal structure of the human cytomegalovirus protease catalytic domain has been determined by X-ray diffraction. The structure defines a new class of serine protease with respect to global-fold topology and has a catalytic triad consisting of Ser-132, His-63, and His-157 in contrast with the Ser-His-Asp triads found in other serine proteases. However, catalytic machinery for activating the serine nucleophile and stabilizing a tetrahedral transition state is oriented similarly to that for members of the trypsin-like and subtilisin-like serine protease families. Formation of the active dimer is mediated primarily by burying a helix of one protomer into a deep cleft in the protein surface of the other.

Characterization of the proteinase specified by varicella-zoster virus gene 33.

“…Among these are the proteinase and assembly proteins, both of which play essential roles in capsid assembly and maturation (Preston et al, 1983 ;Gao et al, 1994). They have been characterized from herpes simplex virus type 1 (HSV-1), human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) (Gibson et al, 1994 ;Donaghy & Jupp, 1995) and the three-dimensional structure of the HCMV proteinase has recently been solved (Chen et al, 1996 ;Qiu et al, 1996 ;Shieh et al, 1996 ;Tong et al, 1996). Sequence homology suggests that VZV genes 33 and 33.5 encode the VZV proteinase and assembly protein respectively (Welch et al, 1991 ;Gibson et al, 1994).…”

Infecciones de Transmisión Sexual en Semen: El Hombre como Vector de Transmisión

“…Herpesviridae, a la cual también pertenecen HSV 1-2 y el virus Epstein-Barr (Chen et al, 1996), aunque HCMV pertenece a la subfamilia Betaherpesvirinae. Su genoma presenta un DNA de doble cadena, lineal, rodeado por una capa proteica que a su vez se encuentra protegida por una bicapa lipidica conteniendo un gran número de glicoproteínas virales.…”

Experiences from the Structure Determination of Human Cytomegalovirus Protease

“…The amino-acid sequences of herpesvirus proteases have no detectable homology to other serine proteases or hydrolases. The crystal structure of HCMV protease has recently been determined in our laboratory by the seleno-methionyl multiple-wavelength anomalous diffraction (MAD) technique (Tong et al, 1996), and in other laboratories by the heavy-atom isomorphous replacement technique (Qiu et al, 1996;Shieh et al, 1996;Chen et al, 1996). It showed that HCMV protease possesses a new polypeptide backbone fold; confirmed that Ser132 and His63 are in close proximity in space; and identified His157 as the possible third member of the catalytic triad.…”