Functional interplay between the B-box 2 and the B30.2(SPRY) domains of TRIM5α

The retroviral restriction factors, TRIM5α and TRIMCyp, consist of RING and B-box 2 domains separated by a coiled coil from carboxy-terminal domains. These carboxy-terminal domains (the B30.2(SPRY) domain in TRIM5α and the cyclophilin A domain in TRIMCyp) recognize the retroviral capsid. Here we show that some B-box 2 changes in TRIM5α, but not in TRIMCyp, resulted in decreased human immunodeficiency virus (HIV-1) capsid binding. The phenotypic effects of these B-box 2 changes on the restriction of retroviral infection depended on the potency of restriction and the affinity of the TRIM5α interaction with the viral capsid, two properties specified by the B30.2(SPRY) domain. Thus, some alterations in the TRIM5α B-box 2 domain apparently affect the orientation or conformation of the B30.2(SPRY) domain, influencing capsid recognition.