Cell surface receptor proteins

Here are two of many known examples of specific cell-cell adhesion. The species-specific reaggregation of dissociated cells of marine sponges (Chapter 1) depends upon a 20-kDa proteoglycan of unique structure209-211 together with a cell surface receptor protein and calcium ions. The recognition of egg cell surfaces by sperm212-214 is species... 

Opsin cem be considered to be a retineddehyde receptor protein, functioning in the same way as cell surface receptor G-proteins (Sakmar, 1998). Like receptor proteins, opsin is a transmembrane protein with seven a -heUccd regions in the transmembrane domain the difference is that opsin spans the intracellular disk membrane of the rod or cone cell, whereas hormone and neurotrcmsmit-ter receptors span the plasma membrane of the cell. The response time of rhodopsin is considerably faster than that of cell surface receptor proteins. 

Theories abound, which relate those two vocabularies, but no one of them has emerged as predominant. Many of the theories suppose the existence of specific receptor sites on the surface of the receptor neurons. One hypothesis posits a set of odors of specific objects (e.g., camphor, sperm, urine, fish) that correspond to pure compounds and represent fundamental submodalities (Beets, 1982). Another (based on molecular biology) proposes dozens—perhaps hundreds—of different types of cell surface receptor proteins, each of which is tuned to a specific odorant compound or class of compounds (Buck, 1996 Zhao et al., 1998). 

The vast majority of drug receptors in the body are proteins. Many are enzymes or cell surface receptors. Proteins are involved in virtually every cellular process and are components in most... 

In addition to the recently isolated cell surface receptor proteins for cell adhesion proteins (10-13), it has become clear that most cell adhesion molecules also recognize other cell surface molecules. Most cell adhesion proteins possess discrete binding sites for collagen, heparin, and ganglioside (or other glycolipids). The avidity of most cell adhesion proteins for one or more species of collagen and the involvement of this interaction in cell adhesion has been reviewed (1) and we will treat this area more thoroughly in a subsequent section. 

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