" Reproduced from Cooper, G. M. (1990). Jones and Bartlett Publ., Boston.

"Oncogenes," p. 238.

Receptor unoccupied

Plasma _


Plasma _


EGF binding

EGF binding

Kina«w inactive

Kinase active

EGF receptor

Kinase consötutively active erb Boncogene

FIGURE 20-8 Mechanism of erbB oncogene activation. The tyrosine kinase activity of the EGF receptor (erbB protooncogene) is regulated by EGF binding; in contrast, the erbB oncogene tyrosine kinase is constitutively active. Reproduced with permission from Cooper G. M. (1990). "Oncogenes," p. 183. Jones and Bartlett Publishers, Boston.

the basis of oncogene activity. Most of the receptors appear to be tyrosine kinases and have the potential enzymatic activity built into their structures. A list of these tyrosine kinases appears in Table 20-2, and the family of tyrosine kinase receptors, some of which are oncogenes, is indicated in Figure 20-7.

As an example, the overexpression of erbB, which was pointed out in a previous discussion of breast cancer, represents a gene encoding information for a insulin receptor EGF precursor

EGF receptor v-fms c-fms high cysteine domains v-erb B


c-mos cell membrane c-mos

cell membrane tyrosine kinase domains

0 0

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